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	$72.55	6.385%	$77.1823	$77.18	$77.20	$77.20
Purchase #2	$214.72	13.758%	$244.2612	$244.26	$244.25	$244.30
Purchase #3	$206.53	6.311%	$219.5641	$219.56	$219.55	$219.60
Purchase #4	$150.31	4.448%	$156.9958	$157.00	$157.00	$157.00
Purchase #5	$158.90	13.871%	$180.941	$180.94	$180.95	$180.90
Purchase #6	$150.65	5.429%	$158.8288	$158.83	$158.85	$158.80
Purchase #7	$105.60	6.498%	$112.4619	$112.46	$112.45	$112.50
7 purchase totals =	$1,059.26		$1,150.2351	$1,150.23	$1,150.25	$1,150.30