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	$61.81	9.363%	$67.5973	$67.60	$67.60	$67.60
Purchase #2	$69.25	9.108%	$75.5573	$75.56	$75.55	$75.60
Purchase #3	$90.38	10.119%	$99.5256	$99.53	$99.55	$99.50
Purchase #4	$33.57	7.722%	$36.1623	$36.16	$36.15	$36.20
Purchase #5	$128.62	11.401%	$143.284	$143.28	$143.30	$143.30
Purchase #6	$206.50	13.492%	$234.361	$234.36	$234.35	$234.40
Purchase #7	$28.69	12.620%	$32.3107	$32.31	$32.30	$32.30
7 purchase totals =	$618.82		$688.7982	$688.80	$688.80	$688.90