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	$42.45	7.480%	$45.6253	$45.63	$45.65	$45.60
Purchase #2	$163.57	12.703%	$184.3483	$184.35	$184.35	$184.30
Purchase #3	$198.92	11.662%	$222.1181	$222.12	$222.10	$222.10
Purchase #4	$113.44	9.353%	$124.05	$124.05	$124.05	$124.10
Purchase #5	$56.77	3.693%	$58.8665	$58.87	$58.85	$58.90
Purchase #6	$111.47	11.631%	$124.4351	$124.44	$124.45	$124.40
Purchase #7	$234.72	6.139%	$249.1295	$249.13	$249.15	$249.10
7 purchase totals =	$921.34		$1,008.5728	$1,008.59	$1,008.60	$1,008.50