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	$151.28	13.687%	$171.9857	$171.99	$172.00	$172.00
Purchase #2	$18.89	10.508%	$20.875	$20.88	$20.90	$20.90
Purchase #3	$201.78	9.717%	$221.387	$221.39	$221.40	$221.40
Purchase #4	$96.82	13.104%	$109.5073	$109.51	$109.50	$109.50
Purchase #5	$23.73	7.194%	$25.4371	$25.44	$25.45	$25.40
Purchase #6	$126.83	9.867%	$139.3443	$139.34	$139.35	$139.30
Purchase #7	$27.54	11.813%	$30.7933	$30.79	$30.80	$30.80
7 purchase totals =	$646.87		$719.3297	$719.34	$719.40	$719.30