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	$55.36	7.172%	$59.3304	$59.33	$59.35	$59.30
Purchase #2	$165.86	11.263%	$184.5408	$184.54	$184.55	$184.50
Purchase #3	$202.25	11.590%	$225.6908	$225.69	$225.70	$225.70
Purchase #4	$173.68	10.864%	$192.5486	$192.55	$192.55	$192.50
Purchase #5	$241.41	9.450%	$264.2232	$264.22	$264.20	$264.20
Purchase #6	$34.84	3.131%	$35.9308	$35.93	$35.95	$35.90
Purchase #7	$127.79	3.325%	$132.039	$132.04	$132.05	$132.00
7 purchase totals =	$1,001.19		$1,094.3036	$1,094.30	$1,094.35	$1,094.10