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	$247.91	4.518%	$259.1106	$259.11	$259.10	$259.10
Purchase #2	$244.32	4.404%	$255.0799	$255.08	$255.10	$255.10
Purchase #3	$214.90	12.211%	$241.1414	$241.14	$241.15	$241.10
Purchase #4	$238.54	10.869%	$264.4669	$264.47	$264.45	$264.50
Purchase #5	$86.40	7.755%	$93.1003	$93.10	$93.10	$93.10
Purchase #6	$53.44	3.393%	$55.2532	$55.25	$55.25	$55.30
Purchase #7	$139.69	13.301%	$158.2702	$158.27	$158.25	$158.30
7 purchase totals =	$1,225.20		$1,326.4225	$1,326.42	$1,326.40	$1,326.50