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	$59.57	11.322%	$66.3145	$66.31	$66.30	$66.30
Purchase #2	$32.74	12.397%	$36.7988	$36.80	$36.80	$36.80
Purchase #3	$196.33	5.360%	$206.8533	$206.85	$206.85	$206.90
Purchase #4	$184.63	13.176%	$208.9568	$208.96	$208.95	$209.00
Purchase #5	$165.96	5.279%	$174.721	$174.72	$174.70	$174.70
Purchase #6	$56.53	4.720%	$59.1982	$59.20	$59.20	$59.20
Purchase #7	$6.68	12.632%	$7.5238	$7.52	$7.50	$7.50
7 purchase totals =	$702.44		$760.3664	$760.36	$760.30	$760.40