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	$240.28	7.766%	$258.9401	$258.94	$258.95	$258.90
Purchase #2	$45.77	4.642%	$47.8946	$47.89	$47.90	$47.90
Purchase #3	$234.80	12.200%	$263.4456	$263.45	$263.45	$263.40
Purchase #4	$229.55	10.347%	$253.3015	$253.30	$253.30	$253.30
Purchase #5	$112.41	13.582%	$127.6775	$127.68	$127.70	$127.70
Purchase #6	$158.67	13.541%	$180.1555	$180.16	$180.15	$180.20
Purchase #7	$12.65	9.847%	$13.8956	$13.90	$13.90	$13.90
7 purchase totals =	$1,034.13		$1,145.3104	$1,145.32	$1,145.35	$1,145.30