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	$208.29	5.816%	$220.4041	$220.40	$220.40	$220.40
Purchase #2	$216.88	12.276%	$243.5042	$243.50	$243.50	$243.50
Purchase #3	$6.80	7.654%	$7.3205	$7.32	$7.30	$7.30
Purchase #4	$133.71	11.243%	$148.743	$148.74	$148.75	$148.70
Purchase #5	$10.48	3.520%	$10.8489	$10.85	$10.85	$10.80
Purchase #6	$51.92	4.460%	$54.2356	$54.24	$54.25	$54.20
Purchase #7	$39.94	8.657%	$43.3976	$43.40	$43.40	$43.40
7 purchase totals =	$668.02		$728.4539	$728.45	$728.45	$728.30