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	$191.26	11.617%	$213.4787	$213.48	$213.50	$213.50
Purchase #2	$126.31	10.367%	$139.4046	$139.40	$139.40	$139.40
Purchase #3	$185.61	12.682%	$209.1491	$209.15	$209.15	$209.10
Purchase #4	$91.61	9.654%	$100.454	$100.45	$100.45	$100.50
Purchase #5	$156.71	13.150%	$177.3174	$177.32	$177.30	$177.30
Purchase #6	$141.76	3.486%	$146.7018	$146.70	$146.70	$146.70
Purchase #7	$134.28	5.157%	$141.2048	$141.20	$141.20	$141.20
7 purchase totals =	$1,027.54		$1,127.7104	$1,127.70	$1,127.70	$1,127.70