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	$28.37	12.148%	$31.8164	$31.82	$31.80	$31.80
Purchase #2	$69.67	6.107%	$73.9247	$73.92	$73.90	$73.90
Purchase #3	$142.82	9.159%	$155.9009	$155.90	$155.90	$155.90
Purchase #4	$231.71	10.770%	$256.6652	$256.67	$256.65	$256.70
Purchase #5	$132.87	10.424%	$146.7204	$146.72	$146.70	$146.70
Purchase #6	$232.63	13.172%	$263.272	$263.27	$263.25	$263.30
Purchase #7	$67.40	11.659%	$75.2582	$75.26	$75.25	$75.30
7 purchase totals =	$905.47		$1,003.5578	$1,003.56	$1,003.45	$1,003.60