Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$234.56	12.538%	$263.9691	$263.97	$263.95	$264.00
Purchase #2	$224.82	8.395%	$243.6936	$243.69	$243.70	$243.70
Purchase #3	$177.98	10.568%	$196.7889	$196.79	$196.80	$196.80
Purchase #4	$240.27	10.174%	$264.7151	$264.72	$264.70	$264.70
Purchase #5	$247.62	7.216%	$265.4883	$265.49	$265.50	$265.50
Purchase #6	$177.38	12.874%	$200.2159	$200.22	$200.20	$200.20
Purchase #7	$101.94	10.416%	$112.5581	$112.56	$112.55	$112.60
7 purchase totals =	$1,404.57		$1,547.4290	$1,547.44	$1,547.40	$1,547.50