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	$174.82	8.697%	$190.0241	$190.02	$190.00	$190.00
Purchase #2	$85.80	9.285%	$93.7665	$93.77	$93.75	$93.80
Purchase #3	$156.92	10.115%	$172.7925	$172.79	$172.80	$172.80
Purchase #4	$21.73	11.633%	$24.2579	$24.26	$24.25	$24.30
Purchase #5	$90.74	10.767%	$100.51	$100.51	$100.50	$100.50
Purchase #6	$166.83	7.838%	$179.9061	$179.91	$179.90	$179.90
Purchase #7	$129.90	13.323%	$147.2066	$147.21	$147.20	$147.20
7 purchase totals =	$826.74		$908.4637	$908.47	$908.40	$908.50