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	$135.33	7.601%	$145.6164	$145.62	$145.60	$145.60
Purchase #2	$56.72	5.246%	$59.6955	$59.70	$59.70	$59.70
Purchase #3	$223.88	12.685%	$252.2792	$252.28	$252.30	$252.30
Purchase #4	$117.61	12.765%	$132.6229	$132.62	$132.60	$132.60
Purchase #5	$156.33	6.802%	$166.9636	$166.96	$166.95	$167.00
Purchase #6	$90.54	4.356%	$94.4839	$94.48	$94.50	$94.50
Purchase #7	$64.37	10.796%	$71.3194	$71.32	$71.30	$71.30
7 purchase totals =	$844.78		$922.9809	$922.98	$922.95	$923.00