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	$237.79	10.778%	$263.419	$263.42	$263.40	$263.40
Purchase #2	$201.77	8.511%	$218.9426	$218.94	$218.95	$218.90
Purchase #3	$175.53	3.297%	$181.3172	$181.32	$181.30	$181.30
Purchase #4	$207.30	12.627%	$233.4758	$233.48	$233.50	$233.50
Purchase #5	$53.44	3.425%	$55.2703	$55.27	$55.25	$55.30
Purchase #6	$158.78	11.304%	$176.7285	$176.73	$176.75	$176.70
Purchase #7	$82.67	8.218%	$89.4638	$89.46	$89.45	$89.50
7 purchase totals =	$1,117.28		$1,218.6172	$1,218.62	$1,218.60	$1,218.60