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	$56.58	11.753%	$63.2298	$63.23	$63.25	$63.20
Purchase #2	$189.52	11.294%	$210.9244	$210.92	$210.90	$210.90
Purchase #3	$157.91	8.521%	$171.3655	$171.37	$171.35	$171.40
Purchase #4	$106.67	4.403%	$111.3667	$111.37	$111.35	$111.40
Purchase #5	$158.79	9.751%	$174.2736	$174.27	$174.25	$174.30
Purchase #6	$213.82	9.578%	$234.2997	$234.30	$234.30	$234.30
Purchase #7	$120.48	4.774%	$126.2317	$126.23	$126.25	$126.20
7 purchase totals =	$1,003.77		$1,091.6914	$1,091.69	$1,091.65	$1,091.70