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	$223.31	13.689%	$253.8789	$253.88	$253.90	$253.90
Purchase #2	$249.81	7.765%	$269.2077	$269.21	$269.20	$269.20
Purchase #3	$61.67	12.684%	$69.4922	$69.49	$69.50	$69.50
Purchase #4	$38.75	4.318%	$40.4232	$40.42	$40.40	$40.40
Purchase #5	$147.29	12.347%	$165.4759	$165.48	$165.50	$165.50
Purchase #6	$142.85	5.326%	$150.4582	$150.46	$150.45	$150.50
Purchase #7	$137.26	5.850%	$145.2897	$145.29	$145.30	$145.30
7 purchase totals =	$1,000.94		$1,094.2258	$1,094.23	$1,094.25	$1,094.30