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	$79.51	3.123%	$81.9931	$81.99	$82.00	$82.00
Purchase #2	$163.62	10.781%	$181.2599	$181.26	$181.25	$181.30
Purchase #3	$65.56	8.126%	$70.8874	$70.89	$70.90	$70.90
Purchase #4	$168.25	9.635%	$184.4609	$184.46	$184.45	$184.50
Purchase #5	$130.92	7.613%	$140.8869	$140.89	$140.90	$140.90
Purchase #6	$224.85	3.761%	$233.3066	$233.31	$233.30	$233.30
Purchase #7	$49.98	13.601%	$56.7778	$56.78	$56.80	$56.80
7 purchase totals =	$882.69		$949.5726	$949.58	$949.60	$949.70