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	$176.88	13.207%	$200.2405	$200.24	$200.25	$200.20
Purchase #2	$240.83	10.355%	$265.7679	$265.77	$265.75	$265.80
Purchase #3	$125.50	4.679%	$131.3721	$131.37	$131.35	$131.40
Purchase #4	$106.36	4.807%	$111.4727	$111.47	$111.45	$111.50
Purchase #5	$44.61	6.441%	$47.4833	$47.48	$47.50	$47.50
Purchase #6	$107.35	7.644%	$115.5558	$115.56	$115.55	$115.60
Purchase #7	$244.84	12.559%	$275.5895	$275.59	$275.60	$275.60
7 purchase totals =	$1,046.37		$1,147.4818	$1,147.48	$1,147.45	$1,147.60