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	$166.36	3.590%	$172.3323	$172.33	$172.35	$172.30
Purchase #2	$31.28	3.833%	$32.479	$32.48	$32.50	$32.50
Purchase #3	$158.73	8.826%	$172.7395	$172.74	$172.75	$172.70
Purchase #4	$48.96	3.296%	$50.5737	$50.57	$50.55	$50.60
Purchase #5	$155.38	8.451%	$168.5112	$168.51	$168.50	$168.50
Purchase #6	$60.68	11.151%	$67.4464	$67.45	$67.45	$67.40
Purchase #7	$112.48	9.371%	$123.0205	$123.02	$123.00	$123.00
7 purchase totals =	$733.87		$787.1026	$787.10	$787.10	$787.00