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	$164.42	11.235%	$182.8926	$182.89	$182.90	$182.90
Purchase #2	$243.33	8.854%	$264.8744	$264.87	$264.85	$264.90
Purchase #3	$149.46	12.199%	$167.6926	$167.69	$167.70	$167.70
Purchase #4	$211.79	5.586%	$223.6206	$223.62	$223.60	$223.60
Purchase #5	$144.43	9.277%	$157.8288	$157.83	$157.85	$157.80
Purchase #6	$16.61	12.160%	$18.6298	$18.63	$18.65	$18.60
Purchase #7	$134.69	3.641%	$139.5941	$139.59	$139.60	$139.60
7 purchase totals =	$1,064.73		$1,155.1329	$1,155.12	$1,155.15	$1,155.10