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	$202.49	4.142%	$210.8771	$210.88	$210.90	$210.90
Purchase #2	$150.72	5.665%	$159.2583	$159.26	$159.25	$159.30
Purchase #3	$246.71	5.324%	$259.8448	$259.84	$259.85	$259.80
Purchase #4	$250.82	5.439%	$264.4621	$264.46	$264.45	$264.50
Purchase #5	$69.27	4.726%	$72.5437	$72.54	$72.55	$72.50
Purchase #6	$188.92	8.721%	$205.3957	$205.40	$205.40	$205.40
Purchase #7	$168.89	5.532%	$178.233	$178.23	$178.25	$178.20
7 purchase totals =	$1,277.82		$1,350.6147	$1,350.61	$1,350.65	$1,350.60