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	$53.86	13.439%	$61.0982	$61.10	$61.10	$61.10
Purchase #2	$169.71	3.227%	$175.1865	$175.19	$175.20	$175.20
Purchase #3	$89.77	11.740%	$100.309	$100.31	$100.30	$100.30
Purchase #4	$144.75	5.445%	$152.6316	$152.63	$152.65	$152.60
Purchase #5	$29.86	4.584%	$31.2288	$31.23	$31.25	$31.20
Purchase #6	$205.61	7.508%	$221.0472	$221.05	$221.05	$221.00
Purchase #7	$30.33	5.787%	$32.0852	$32.09	$32.10	$32.10
7 purchase totals =	$723.89		$773.5865	$773.60	$773.65	$773.50