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	$74.84	9.262%	$81.7717	$81.77	$81.75	$81.80
Purchase #2	$173.54	13.340%	$196.6902	$196.69	$196.70	$196.70
Purchase #3	$81.76	9.344%	$89.3997	$89.40	$89.40	$89.40
Purchase #4	$184.67	13.788%	$210.1323	$210.13	$210.15	$210.10
Purchase #5	$149.59	10.316%	$165.0217	$165.02	$165.00	$165.00
Purchase #6	$180.45	11.350%	$200.9311	$200.93	$200.95	$200.90
Purchase #7	$245.94	7.580%	$264.5823	$264.58	$264.60	$264.60
7 purchase totals =	$1,090.79		$1,208.5290	$1,208.52	$1,208.55	$1,208.50