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	$57.25	4.670%	$59.9236	$59.92	$59.90	$59.90
Purchase #2	$129.74	6.830%	$138.6012	$138.60	$138.60	$138.60
Purchase #3	$228.76	10.298%	$252.3177	$252.32	$252.30	$252.30
Purchase #4	$148.48	5.661%	$156.8855	$156.89	$156.90	$156.90
Purchase #5	$118.86	7.151%	$127.3597	$127.36	$127.35	$127.40
Purchase #6	$82.77	6.715%	$88.328	$88.33	$88.35	$88.30
Purchase #7	$223.65	9.463%	$244.814	$244.81	$244.80	$244.80
7 purchase totals =	$989.51		$1,068.2297	$1,068.23	$1,068.20	$1,068.20