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	$200.98	8.670%	$218.405	$218.41	$218.40	$218.40
Purchase #2	$56.70	5.600%	$59.8752	$59.88	$59.90	$59.90
Purchase #3	$138.65	5.361%	$146.083	$146.08	$146.10	$146.10
Purchase #4	$135.54	7.764%	$146.0633	$146.06	$146.05	$146.10
Purchase #5	$246.48	5.539%	$260.1325	$260.13	$260.15	$260.10
Purchase #6	$153.38	10.244%	$169.0922	$169.09	$169.10	$169.10
Purchase #7	$48.63	13.456%	$55.1737	$55.17	$55.15	$55.20
7 purchase totals =	$980.36		$1,054.8249	$1,054.82	$1,054.85	$1,054.90