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	$241.44	11.237%	$268.5706	$268.57	$268.55	$268.60
Purchase #2	$71.56	12.759%	$80.6903	$80.69	$80.70	$80.70
Purchase #3	$80.52	6.325%	$85.6129	$85.61	$85.60	$85.60
Purchase #4	$26.82	4.582%	$28.0489	$28.05	$28.05	$28.00
Purchase #5	$200.25	12.616%	$225.5135	$225.51	$225.50	$225.50
Purchase #6	$144.44	5.558%	$152.468	$152.47	$152.45	$152.50
Purchase #7	$84.67	12.505%	$95.258	$95.26	$95.25	$95.30
7 purchase totals =	$849.70		$936.1622	$936.16	$936.10	$936.20