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	$93.89	12.142%	$105.2901	$105.29	$105.30	$105.30
Purchase #2	$243.57	6.663%	$259.7991	$259.80	$259.80	$259.80
Purchase #3	$166.43	5.612%	$175.7701	$175.77	$175.75	$175.80
Purchase #4	$85.50	6.367%	$90.9438	$90.94	$90.95	$90.90
Purchase #5	$64.53	13.543%	$73.2693	$73.27	$73.25	$73.30
Purchase #6	$102.86	8.387%	$111.4869	$111.49	$111.50	$111.50
Purchase #7	$239.89	8.826%	$261.0627	$261.06	$261.05	$261.10
7 purchase totals =	$996.67		$1,077.6220	$1,077.62	$1,077.60	$1,077.70