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	$98.86	12.805%	$111.519	$111.52	$111.50	$111.50
Purchase #2	$56.84	7.506%	$61.1064	$61.11	$61.10	$61.10
Purchase #3	$114.38	12.504%	$128.6821	$128.68	$128.70	$128.70
Purchase #4	$224.48	12.704%	$252.9979	$253.00	$253.00	$253.00
Purchase #5	$119.50	4.723%	$125.144	$125.14	$125.15	$125.10
Purchase #6	$101.98	8.872%	$111.0277	$111.03	$111.05	$111.00
Purchase #7	$12.26	11.170%	$13.6294	$13.63	$13.65	$13.60
7 purchase totals =	$728.30		$804.1065	$804.11	$804.15	$804.00