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	$98.30	7.123%	$105.3019	$105.30	$105.30	$105.30
Purchase #2	$36.26	4.322%	$37.8272	$37.83	$37.85	$37.80
Purchase #3	$148.78	10.345%	$164.1713	$164.17	$164.15	$164.20
Purchase #4	$149.79	7.652%	$161.2519	$161.25	$161.25	$161.30
Purchase #5	$244.78	10.534%	$270.5651	$270.57	$270.55	$270.60
Purchase #6	$7.76	13.168%	$8.7818	$8.78	$8.80	$8.80
Purchase #7	$236.51	9.715%	$259.4869	$259.49	$259.50	$259.50
7 purchase totals =	$922.18		$1,007.3861	$1,007.39	$1,007.40	$1,007.50