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	$158.41	11.242%	$176.2185	$176.22	$176.20	$176.20
Purchase #2	$193.98	3.282%	$200.3464	$200.35	$200.35	$200.30
Purchase #3	$141.52	7.165%	$151.6599	$151.66	$151.65	$151.70
Purchase #4	$40.35	5.257%	$42.4712	$42.47	$42.45	$42.50
Purchase #5	$89.68	12.228%	$100.6461	$100.65	$100.65	$100.60
Purchase #6	$244.73	9.535%	$268.065	$268.07	$268.05	$268.10
Purchase #7	$157.98	9.369%	$172.7811	$172.78	$172.80	$172.80
7 purchase totals =	$1,026.65		$1,112.1882	$1,112.20	$1,112.15	$1,112.20