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	$61.95	13.103%	$70.0673	$70.07	$70.05	$70.10
Purchase #2	$8.47	12.570%	$9.5347	$9.53	$9.55	$9.50
Purchase #3	$176.93	6.269%	$188.0217	$188.02	$188.00	$188.00
Purchase #4	$73.82	11.362%	$82.2074	$82.21	$82.20	$82.20
Purchase #5	$6.80	10.121%	$7.4882	$7.49	$7.50	$7.50
Purchase #6	$64.50	12.401%	$72.4986	$72.50	$72.50	$72.50
Purchase #7	$80.44	13.194%	$91.0533	$91.05	$91.05	$91.10
7 purchase totals =	$472.91		$520.8712	$520.87	$520.85	$520.90