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	$114.38	8.254%	$123.8209	$123.82	$123.80	$123.80
Purchase #2	$244.70	3.811%	$254.0255	$254.03	$254.05	$254.00
Purchase #3	$243.65	5.136%	$256.1639	$256.16	$256.15	$256.20
Purchase #4	$17.58	10.300%	$19.3907	$19.39	$19.40	$19.40
Purchase #5	$195.56	13.592%	$222.1405	$222.14	$222.15	$222.10
Purchase #6	$249.51	9.150%	$272.3402	$272.34	$272.35	$272.30
Purchase #7	$210.58	11.661%	$235.1357	$235.14	$235.15	$235.10
7 purchase totals =	$1,275.96		$1,383.0174	$1,383.02	$1,383.05	$1,382.90