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	$152.93	11.651%	$170.7479	$170.75	$170.75	$170.70
Purchase #2	$166.89	3.435%	$172.6227	$172.62	$172.60	$172.60
Purchase #3	$53.32	4.263%	$55.593	$55.59	$55.60	$55.60
Purchase #4	$227.79	13.475%	$258.4847	$258.48	$258.50	$258.50
Purchase #5	$34.50	12.690%	$38.8781	$38.88	$38.90	$38.90
Purchase #6	$65.94	7.357%	$70.7912	$70.79	$70.80	$70.80
Purchase #7	$233.79	3.668%	$242.3654	$242.37	$242.35	$242.40
7 purchase totals =	$935.16		$1,009.4830	$1,009.48	$1,009.50	$1,009.50