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	$182.36	10.196%	$200.9534	$200.95	$200.95	$201.00
Purchase #2	$37.92	11.731%	$42.3684	$42.37	$42.35	$42.40
Purchase #3	$223.87	4.570%	$234.1009	$234.10	$234.10	$234.10
Purchase #4	$169.38	11.668%	$189.1433	$189.14	$189.15	$189.10
Purchase #5	$152.51	10.654%	$168.7584	$168.76	$168.75	$168.80
Purchase #6	$229.53	11.717%	$256.424	$256.42	$256.40	$256.40
Purchase #7	$233.69	9.669%	$256.2855	$256.29	$256.30	$256.30
7 purchase totals =	$1,229.26		$1,348.0339	$1,348.03	$1,348.00	$1,348.10