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	$105.90	5.388%	$111.6059	$111.61	$111.60	$111.60
Purchase #2	$54.26	9.454%	$59.3897	$59.39	$59.40	$59.40
Purchase #3	$190.30	10.446%	$210.1787	$210.18	$210.20	$210.20
Purchase #4	$194.51	10.691%	$215.3051	$215.31	$215.30	$215.30
Purchase #5	$216.26	10.251%	$238.4288	$238.43	$238.45	$238.40
Purchase #6	$148.99	7.591%	$160.2998	$160.30	$160.30	$160.30
Purchase #7	$125.71	11.508%	$140.1767	$140.18	$140.20	$140.20
7 purchase totals =	$1,035.93		$1,135.3847	$1,135.40	$1,135.45	$1,135.40