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	$201.26	13.122%	$227.6693	$227.67	$227.65	$227.70
Purchase #2	$33.65	11.544%	$37.5346	$37.53	$37.55	$37.50
Purchase #3	$245.41	13.489%	$278.5134	$278.51	$278.50	$278.50
Purchase #4	$139.97	9.528%	$153.3063	$153.31	$153.30	$153.30
Purchase #5	$189.43	13.532%	$215.0637	$215.06	$215.05	$215.10
Purchase #6	$157.33	5.389%	$165.8085	$165.81	$165.80	$165.80
Purchase #7	$221.28	4.423%	$231.0672	$231.07	$231.05	$231.10
7 purchase totals =	$1,188.33		$1,308.9630	$1,308.96	$1,308.90	$1,309.00