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	$152.90	8.444%	$165.8109	$165.81	$165.80	$165.80
Purchase #2	$54.74	13.235%	$61.9848	$61.98	$62.00	$62.00
Purchase #3	$186.41	7.183%	$199.7998	$199.80	$199.80	$199.80
Purchase #4	$159.31	4.573%	$166.5952	$166.60	$166.60	$166.60
Purchase #5	$161.46	3.350%	$166.8689	$166.87	$166.85	$166.90
Purchase #6	$34.59	7.548%	$37.2009	$37.20	$37.20	$37.20
Purchase #7	$207.57	13.330%	$235.2391	$235.24	$235.25	$235.20
7 purchase totals =	$956.98		$1,033.4996	$1,033.50	$1,033.50	$1,033.50