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	$185.87	5.555%	$196.1951	$196.20	$196.20	$196.20
Purchase #2	$172.33	9.645%	$188.9512	$188.95	$188.95	$189.00
Purchase #3	$57.53	4.664%	$60.2132	$60.21	$60.20	$60.20
Purchase #4	$182.49	4.164%	$190.0889	$190.09	$190.10	$190.10
Purchase #5	$87.81	5.853%	$92.9495	$92.95	$92.95	$92.90
Purchase #6	$62.45	8.142%	$67.5347	$67.53	$67.55	$67.50
Purchase #7	$249.92	3.537%	$258.7597	$258.76	$258.75	$258.80
7 purchase totals =	$998.40		$1,054.6923	$1,054.69	$1,054.70	$1,054.70