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	$118.61	10.668%	$131.2633	$131.26	$131.25	$131.30
Purchase #2	$102.89	9.787%	$112.9598	$112.96	$112.95	$113.00
Purchase #3	$192.96	8.458%	$209.2806	$209.28	$209.30	$209.30
Purchase #4	$238.96	10.638%	$264.3806	$264.38	$264.40	$264.40
Purchase #5	$115.38	13.304%	$130.7302	$130.73	$130.75	$130.70
Purchase #6	$94.60	6.163%	$100.4302	$100.43	$100.45	$100.40
Purchase #7	$122.49	5.401%	$129.1057	$129.11	$129.10	$129.10
7 purchase totals =	$985.89		$1,078.1504	$1,078.15	$1,078.20	$1,078.20