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	$67.43	11.263%	$75.0246	$75.02	$75.00	$75.00
Purchase #2	$189.62	7.278%	$203.4205	$203.42	$203.40	$203.40
Purchase #3	$37.57	8.791%	$40.8728	$40.87	$40.85	$40.90
Purchase #4	$109.30	7.170%	$117.1368	$117.14	$117.15	$117.10
Purchase #5	$247.89	12.172%	$278.0632	$278.06	$278.05	$278.10
Purchase #6	$116.78	5.797%	$123.5497	$123.55	$123.55	$123.50
Purchase #7	$90.90	12.814%	$102.5479	$102.55	$102.55	$102.50
7 purchase totals =	$859.49		$940.6155	$940.61	$940.55	$940.50