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	$89.34	13.732%	$101.6082	$101.61	$101.60	$101.60
Purchase #2	$218.71	7.624%	$235.3845	$235.38	$235.40	$235.40
Purchase #3	$85.86	6.220%	$91.2005	$91.20	$91.20	$91.20
Purchase #4	$137.51	3.473%	$142.2857	$142.29	$142.30	$142.30
Purchase #5	$153.29	7.673%	$165.0519	$165.05	$165.05	$165.10
Purchase #6	$59.65	3.689%	$61.8505	$61.85	$61.85	$61.90
Purchase #7	$53.52	13.173%	$60.5702	$60.57	$60.55	$60.60
7 purchase totals =	$797.88		$857.9515	$857.95	$857.95	$858.10