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	$75.57	3.767%	$78.4167	$78.42	$78.40	$78.40
Purchase #2	$107.48	11.706%	$120.0616	$120.06	$120.05	$120.10
Purchase #3	$140.86	12.402%	$158.3295	$158.33	$158.35	$158.30
Purchase #4	$218.96	11.197%	$243.477	$243.48	$243.50	$243.50
Purchase #5	$123.76	5.784%	$130.9183	$130.92	$130.90	$130.90
Purchase #6	$120.91	10.700%	$133.8474	$133.85	$133.85	$133.80
Purchase #7	$141.31	11.821%	$158.0143	$158.01	$158.00	$158.00
7 purchase totals =	$928.85		$1,023.0648	$1,023.07	$1,023.05	$1,023.00