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	$215.52	6.847%	$230.2767	$230.28	$230.30	$230.30
Purchase #2	$97.74	9.362%	$106.8904	$106.89	$106.90	$106.90
Purchase #3	$86.59	5.336%	$91.2104	$91.21	$91.20	$91.20
Purchase #4	$69.97	11.563%	$78.0606	$78.06	$78.05	$78.10
Purchase #5	$203.45	10.692%	$225.2029	$225.20	$225.20	$225.20
Purchase #6	$105.69	5.349%	$111.3434	$111.34	$111.35	$111.30
Purchase #7	$229.73	10.506%	$253.8654	$253.87	$253.85	$253.90
7 purchase totals =	$1,008.69		$1,096.8498	$1,096.85	$1,096.85	$1,096.90