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	$157.72	10.813%	$174.7743	$174.77	$174.75	$174.80
Purchase #2	$37.64	12.342%	$42.2855	$42.29	$42.30	$42.30
Purchase #3	$221.76	4.769%	$232.3357	$232.34	$232.35	$232.30
Purchase #4	$111.75	10.869%	$123.8961	$123.90	$123.90	$123.90
Purchase #5	$65.30	9.742%	$71.6615	$71.66	$71.65	$71.70
Purchase #6	$143.49	4.156%	$149.4534	$149.45	$149.45	$149.50
Purchase #7	$154.26	11.198%	$171.534	$171.53	$171.55	$171.50
7 purchase totals =	$891.92		$965.9405	$965.94	$965.95	$966.00