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	$124.77	7.771%	$134.4659	$134.47	$134.45	$134.50
Purchase #2	$171.43	13.501%	$194.5748	$194.57	$194.55	$194.60
Purchase #3	$104.75	11.663%	$116.967	$116.97	$116.95	$117.00
Purchase #4	$185.45	3.478%	$191.9	$191.90	$191.90	$191.90
Purchase #5	$161.34	3.308%	$166.6771	$166.68	$166.70	$166.70
Purchase #6	$170.58	12.222%	$191.4283	$191.43	$191.45	$191.40
Purchase #7	$93.84	7.420%	$100.8029	$100.80	$100.80	$100.80
7 purchase totals =	$1,012.16		$1,096.8160	$1,096.82	$1,096.80	$1,096.90