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	$154.48	3.261%	$159.5176	$159.52	$159.50	$159.50
Purchase #2	$145.59	11.166%	$161.8466	$161.85	$161.85	$161.80
Purchase #3	$79.71	9.781%	$87.5064	$87.51	$87.50	$87.50
Purchase #4	$188.42	8.540%	$204.5111	$204.51	$204.50	$204.50
Purchase #5	$141.37	5.510%	$149.1595	$149.16	$149.15	$149.20
Purchase #6	$180.46	11.118%	$200.5235	$200.52	$200.50	$200.50
Purchase #7	$135.94	3.616%	$140.8556	$140.86	$140.85	$140.90
7 purchase totals =	$1,025.97		$1,103.9203	$1,103.93	$1,103.85	$1,103.90