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	$143.59	11.528%	$160.1431	$160.14	$160.15	$160.10
Purchase #2	$122.98	13.703%	$139.8319	$139.83	$139.85	$139.80
Purchase #3	$204.81	11.219%	$227.7876	$227.79	$227.80	$227.80
Purchase #4	$84.37	8.827%	$91.8173	$91.82	$91.80	$91.80
Purchase #5	$205.59	11.796%	$229.8414	$229.84	$229.85	$229.80
Purchase #6	$66.27	5.448%	$69.8804	$69.88	$69.90	$69.90
Purchase #7	$76.69	12.833%	$86.5316	$86.53	$86.55	$86.50
7 purchase totals =	$904.30		$1,005.8333	$1,005.83	$1,005.90	$1,005.70