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	$55.55	6.573%	$59.2013	$59.20	$59.20	$59.20
Purchase #2	$145.82	7.486%	$156.7361	$156.74	$156.75	$156.70
Purchase #3	$128.97	13.490%	$146.3681	$146.37	$146.35	$146.40
Purchase #4	$166.38	11.794%	$186.0029	$186.00	$186.00	$186.00
Purchase #5	$168.47	12.577%	$189.6585	$189.66	$189.65	$189.70
Purchase #6	$243.42	8.615%	$264.3906	$264.39	$264.40	$264.40
Purchase #7	$154.91	6.557%	$165.0674	$165.07	$165.05	$165.10
7 purchase totals =	$1,063.52		$1,167.4249	$1,167.43	$1,167.40	$1,167.50