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	$110.48	13.700%	$125.6158	$125.62	$125.60	$125.60
Purchase #2	$214.57	3.747%	$222.6099	$222.61	$222.60	$222.60
Purchase #3	$173.86	5.454%	$183.3423	$183.34	$183.35	$183.30
Purchase #4	$225.37	4.127%	$234.671	$234.67	$234.65	$234.70
Purchase #5	$19.93	7.201%	$21.3652	$21.37	$21.35	$21.40
Purchase #6	$185.72	5.541%	$196.0107	$196.01	$196.00	$196.00
Purchase #7	$184.69	8.569%	$200.5161	$200.52	$200.50	$200.50
7 purchase totals =	$1,114.62		$1,184.1310	$1,184.14	$1,184.05	$1,184.10