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	$151.65	3.225%	$156.5407	$156.54	$156.55	$156.50
Purchase #2	$6.41	9.816%	$7.0392	$7.04	$7.05	$7.00
Purchase #3	$103.55	10.261%	$114.1753	$114.18	$114.20	$114.20
Purchase #4	$221.98	11.206%	$246.8551	$246.86	$246.85	$246.90
Purchase #5	$174.66	12.477%	$196.4523	$196.45	$196.45	$196.50
Purchase #6	$243.91	13.700%	$277.3257	$277.33	$277.35	$277.30
Purchase #7	$28.73	3.744%	$29.8057	$29.81	$29.80	$29.80
7 purchase totals =	$930.89		$1,028.1940	$1,028.21	$1,028.25	$1,028.20