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	$206.96	9.573%	$226.7723	$226.77	$226.75	$226.80
Purchase #2	$93.69	6.643%	$99.9138	$99.91	$99.90	$99.90
Purchase #3	$225.31	13.678%	$256.1279	$256.13	$256.15	$256.10
Purchase #4	$56.48	8.240%	$61.134	$61.13	$61.15	$61.10
Purchase #5	$249.71	7.670%	$268.8628	$268.86	$268.85	$268.90
Purchase #6	$36.63	4.836%	$38.4014	$38.40	$38.40	$38.40
Purchase #7	$196.62	7.690%	$211.7401	$211.74	$211.75	$211.70
7 purchase totals =	$1,065.40		$1,162.9523	$1,162.94	$1,162.95	$1,162.90