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	$157.30	8.406%	$170.5226	$170.52	$170.50	$170.50
Purchase #2	$17.58	12.596%	$19.7944	$19.79	$19.80	$19.80
Purchase #3	$179.56	7.749%	$193.4741	$193.47	$193.45	$193.50
Purchase #4	$112.71	5.851%	$119.3047	$119.30	$119.30	$119.30
Purchase #5	$85.68	5.445%	$90.3453	$90.35	$90.35	$90.30
Purchase #6	$115.95	10.270%	$127.8581	$127.86	$127.85	$127.90
Purchase #7	$62.89	11.447%	$70.089	$70.09	$70.10	$70.10
7 purchase totals =	$731.67		$791.3882	$791.38	$791.35	$791.40