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	$70.49	4.306%	$73.5253	$73.53	$73.55	$73.50
Purchase #2	$160.97	12.397%	$180.9255	$180.93	$180.95	$180.90
Purchase #3	$72.27	8.345%	$78.3009	$78.30	$78.30	$78.30
Purchase #4	$102.44	11.871%	$114.6007	$114.60	$114.60	$114.60
Purchase #5	$70.83	12.788%	$79.8877	$79.89	$79.90	$79.90
Purchase #6	$137.79	12.703%	$155.2935	$155.29	$155.30	$155.30
Purchase #7	$53.69	13.684%	$61.0369	$61.04	$61.05	$61.00
7 purchase totals =	$668.48		$743.5705	$743.58	$743.65	$743.50