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	$184.58	5.730%	$195.1564	$195.16	$195.15	$195.20
Purchase #2	$74.72	10.437%	$82.5185	$82.52	$82.50	$82.50
Purchase #3	$179.69	13.865%	$204.604	$204.60	$204.60	$204.60
Purchase #4	$144.30	5.790%	$152.655	$152.66	$152.65	$152.70
Purchase #5	$68.99	13.775%	$78.4934	$78.49	$78.50	$78.50
Purchase #6	$237.44	12.591%	$267.3361	$267.34	$267.35	$267.30
Purchase #7	$92.97	6.613%	$99.1181	$99.12	$99.10	$99.10
7 purchase totals =	$982.69		$1,079.8815	$1,079.89	$1,079.85	$1,079.90