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	$234.51	13.764%	$266.788	$266.79	$266.80	$266.80
Purchase #2	$52.75	8.858%	$57.4226	$57.42	$57.40	$57.40
Purchase #3	$249.55	6.144%	$264.8824	$264.88	$264.90	$264.90
Purchase #4	$139.70	11.842%	$156.2433	$156.24	$156.25	$156.20
Purchase #5	$33.39	10.485%	$36.8909	$36.89	$36.90	$36.90
Purchase #6	$99.81	5.272%	$105.072	$105.07	$105.05	$105.10
Purchase #7	$196.73	5.452%	$207.4557	$207.46	$207.45	$207.50
7 purchase totals =	$1,006.44		$1,094.7549	$1,094.75	$1,094.75	$1,094.80