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	$107.37	5.149%	$112.8985	$112.90	$112.90	$112.90
Purchase #2	$159.71	9.114%	$174.266	$174.27	$174.25	$174.30
Purchase #3	$31.42	6.301%	$33.3998	$33.40	$33.40	$33.40
Purchase #4	$208.92	7.113%	$223.7805	$223.78	$223.80	$223.80
Purchase #5	$111.34	11.434%	$124.0706	$124.07	$124.05	$124.10
Purchase #6	$135.85	11.259%	$151.1454	$151.15	$151.15	$151.10
Purchase #7	$178.32	12.547%	$200.6938	$200.69	$200.70	$200.70
7 purchase totals =	$932.93		$1,020.2546	$1,020.26	$1,020.25	$1,020.30