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	$62.30	7.574%	$67.0186	$67.02	$67.00	$67.00
Purchase #2	$20.57	4.714%	$21.5397	$21.54	$21.55	$21.50
Purchase #3	$236.87	13.289%	$268.3477	$268.35	$268.35	$268.30
Purchase #4	$85.27	9.614%	$93.4679	$93.47	$93.45	$93.50
Purchase #5	$51.39	7.224%	$55.1024	$55.10	$55.10	$55.10
Purchase #6	$68.92	3.256%	$71.164	$71.16	$71.15	$71.20
Purchase #7	$155.37	6.400%	$165.3137	$165.31	$165.30	$165.30
7 purchase totals =	$680.69		$741.9540	$741.95	$741.90	$741.90