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	$72.81	11.790%	$81.3943	$81.39	$81.40	$81.40
Purchase #2	$79.83	7.387%	$85.727	$85.73	$85.75	$85.70
Purchase #3	$219.69	4.511%	$229.6002	$229.60	$229.60	$229.60
Purchase #4	$152.86	10.762%	$169.3108	$169.31	$169.30	$169.30
Purchase #5	$217.46	3.358%	$224.7623	$224.76	$224.75	$224.80
Purchase #6	$186.43	5.219%	$196.1598	$196.16	$196.15	$196.20
Purchase #7	$244.50	10.227%	$269.505	$269.51	$269.50	$269.50
7 purchase totals =	$1,173.58		$1,256.4594	$1,256.46	$1,256.45	$1,256.50