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	$151.31	6.774%	$161.5597	$161.56	$161.55	$161.60
Purchase #2	$10.54	13.306%	$11.9425	$11.94	$11.95	$11.90
Purchase #3	$161.45	12.603%	$181.7975	$181.80	$181.80	$181.80
Purchase #4	$78.84	13.650%	$89.6017	$89.60	$89.60	$89.60
Purchase #5	$35.39	5.326%	$37.2749	$37.27	$37.25	$37.30
Purchase #6	$97.74	8.787%	$106.3284	$106.33	$106.35	$106.30
Purchase #7	$75.90	8.308%	$82.2058	$82.21	$82.20	$82.20
7 purchase totals =	$611.17		$670.7105	$670.71	$670.70	$670.70