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	$221.85	7.687%	$238.9036	$238.90	$238.90	$238.90
Purchase #2	$33.51	7.601%	$36.0571	$36.06	$36.05	$36.10
Purchase #3	$98.98	6.216%	$105.1326	$105.13	$105.15	$105.10
Purchase #4	$86.64	6.497%	$92.269	$92.27	$92.25	$92.30
Purchase #5	$248.89	13.799%	$283.2343	$283.23	$283.25	$283.20
Purchase #6	$116.27	9.700%	$127.5482	$127.55	$127.55	$127.50
Purchase #7	$130.85	3.684%	$135.6705	$135.67	$135.65	$135.70
7 purchase totals =	$936.99		$1,018.8153	$1,018.81	$1,018.80	$1,018.80