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	$65.72	7.420%	$70.5964	$70.60	$70.60	$70.60
Purchase #2	$223.58	13.796%	$254.4251	$254.43	$254.45	$254.40
Purchase #3	$125.61	13.746%	$142.8764	$142.88	$142.90	$142.90
Purchase #4	$47.27	10.300%	$52.1388	$52.14	$52.15	$52.10
Purchase #5	$65.83	13.343%	$74.6137	$74.61	$74.60	$74.60
Purchase #6	$93.91	13.233%	$106.3371	$106.34	$106.35	$106.30
Purchase #7	$38.95	7.563%	$41.8958	$41.90	$41.90	$41.90
7 purchase totals =	$660.87		$742.8833	$742.90	$742.95	$742.80