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	$147.52	7.755%	$158.9602	$158.96	$158.95	$159.00
Purchase #2	$9.98	4.630%	$10.4421	$10.44	$10.45	$10.40
Purchase #3	$192.72	10.580%	$213.1098	$213.11	$213.10	$213.10
Purchase #4	$140.90	5.658%	$148.8721	$148.87	$148.85	$148.90
Purchase #5	$29.61	8.274%	$32.0599	$32.06	$32.05	$32.10
Purchase #6	$154.89	10.758%	$171.5531	$171.55	$171.55	$171.60
Purchase #7	$53.97	13.121%	$61.0514	$61.05	$61.05	$61.10
7 purchase totals =	$729.59		$796.0486	$796.04	$796.00	$796.20