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	$203.43	6.146%	$215.9328	$215.93	$215.95	$215.90
Purchase #2	$249.81	5.795%	$264.2865	$264.29	$264.30	$264.30
Purchase #3	$115.97	3.379%	$119.8886	$119.89	$119.90	$119.90
Purchase #4	$72.31	13.449%	$82.035	$82.04	$82.05	$82.00
Purchase #5	$94.48	9.133%	$103.1089	$103.11	$103.10	$103.10
Purchase #6	$177.45	11.389%	$197.6598	$197.66	$197.65	$197.70
Purchase #7	$229.44	9.342%	$250.8743	$250.87	$250.85	$250.90
7 purchase totals =	$1,142.89		$1,233.7859	$1,233.79	$1,233.80	$1,233.80