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	$53.73	5.380%	$56.6207	$56.62	$56.60	$56.60
Purchase #2	$66.86	13.801%	$76.0873	$76.09	$76.10	$76.10
Purchase #3	$146.33	13.650%	$166.304	$166.30	$166.30	$166.30
Purchase #4	$225.80	7.443%	$242.6063	$242.61	$242.60	$242.60
Purchase #5	$87.87	13.552%	$99.7781	$99.78	$99.80	$99.80
Purchase #6	$235.38	13.557%	$267.2905	$267.29	$267.30	$267.30
Purchase #7	$120.63	4.634%	$126.22	$126.22	$126.20	$126.20
7 purchase totals =	$936.60		$1,034.9069	$1,034.91	$1,034.90	$1,034.90