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	$71.47	9.288%	$78.1081	$78.11	$78.10	$78.10
Purchase #2	$97.84	3.567%	$101.33	$101.33	$101.35	$101.30
Purchase #3	$150.70	9.665%	$165.2652	$165.27	$165.25	$165.30
Purchase #4	$206.55	8.694%	$224.5075	$224.51	$224.50	$224.50
Purchase #5	$242.63	9.571%	$265.8521	$265.85	$265.85	$265.90
Purchase #6	$219.93	9.759%	$241.393	$241.39	$241.40	$241.40
Purchase #7	$229.29	13.414%	$260.047	$260.05	$260.05	$260.00
7 purchase totals =	$1,218.41		$1,336.5029	$1,336.51	$1,336.50	$1,336.50