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	$38.41	13.200%	$43.4801	$43.48	$43.50	$43.50
Purchase #2	$126.54	3.247%	$130.6488	$130.65	$130.65	$130.60
Purchase #3	$58.37	8.788%	$63.4996	$63.50	$63.50	$63.50
Purchase #4	$209.28	6.843%	$223.601	$223.60	$223.60	$223.60
Purchase #5	$191.57	11.635%	$213.8592	$213.86	$213.85	$213.90
Purchase #6	$153.42	7.863%	$165.4834	$165.48	$165.50	$165.50
Purchase #7	$172.57	4.736%	$180.7429	$180.74	$180.75	$180.70
7 purchase totals =	$950.16		$1,021.3150	$1,021.31	$1,021.35	$1,021.30