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	$224.88	9.717%	$246.7316	$246.73	$246.75	$246.70
Purchase #2	$189.31	5.812%	$200.3127	$200.31	$200.30	$200.30
Purchase #3	$242.99	6.823%	$259.5692	$259.57	$259.55	$259.60
Purchase #4	$223.27	4.403%	$233.1006	$233.10	$233.10	$233.10
Purchase #5	$60.98	6.244%	$64.7876	$64.79	$64.80	$64.80
Purchase #6	$81.30	11.778%	$90.8755	$90.88	$90.90	$90.90
Purchase #7	$89.58	12.664%	$100.9244	$100.92	$100.90	$100.90
7 purchase totals =	$1,112.31		$1,196.3016	$1,196.30	$1,196.30	$1,196.30