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	$124.73	7.191%	$133.6993	$133.70	$133.70	$133.70
Purchase #2	$86.96	7.213%	$93.2324	$93.23	$93.25	$93.20
Purchase #3	$17.33	10.307%	$19.1162	$19.12	$19.10	$19.10
Purchase #4	$231.87	10.601%	$256.4505	$256.45	$256.45	$256.50
Purchase #5	$69.85	12.437%	$78.5372	$78.54	$78.55	$78.50
Purchase #6	$231.87	13.650%	$263.5203	$263.52	$263.50	$263.50
Purchase #7	$35.57	10.574%	$39.3312	$39.33	$39.35	$39.30
7 purchase totals =	$798.18		$883.8871	$883.89	$883.90	$883.80