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	$199.31	5.672%	$210.6149	$210.61	$210.60	$210.60
Purchase #2	$219.40	6.331%	$233.2902	$233.29	$233.30	$233.30
Purchase #3	$69.85	6.659%	$74.5013	$74.50	$74.50	$74.50
Purchase #4	$42.49	8.530%	$46.1144	$46.11	$46.10	$46.10
Purchase #5	$152.43	9.355%	$166.6898	$166.69	$166.70	$166.70
Purchase #6	$185.81	12.754%	$209.5082	$209.51	$209.50	$209.50
Purchase #7	$102.79	6.594%	$109.568	$109.57	$109.55	$109.60
7 purchase totals =	$972.08		$1,050.2868	$1,050.28	$1,050.25	$1,050.30