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	$55.61	11.483%	$61.9957	$62.00	$62.00	$62.00
Purchase #2	$109.98	12.281%	$123.4866	$123.49	$123.50	$123.50
Purchase #3	$190.88	9.139%	$208.3245	$208.32	$208.30	$208.30
Purchase #4	$206.29	11.282%	$229.5636	$229.56	$229.55	$229.60
Purchase #5	$56.63	4.687%	$59.2842	$59.28	$59.30	$59.30
Purchase #6	$188.34	7.137%	$201.7818	$201.78	$201.80	$201.80
Purchase #7	$17.77	9.561%	$19.469	$19.47	$19.45	$19.50
7 purchase totals =	$825.50		$903.9054	$903.90	$903.90	$904.00