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	$187.32	13.450%	$212.5145	$212.51	$212.50	$212.50
Purchase #2	$65.50	13.148%	$74.1119	$74.11	$74.10	$74.10
Purchase #3	$63.63	12.473%	$71.5666	$71.57	$71.55	$71.60
Purchase #4	$32.56	7.156%	$34.89	$34.89	$34.90	$34.90
Purchase #5	$134.80	5.591%	$142.3367	$142.34	$142.35	$142.30
Purchase #6	$134.74	7.198%	$144.4386	$144.44	$144.45	$144.40
Purchase #7	$91.52	3.322%	$94.5603	$94.56	$94.55	$94.60
7 purchase totals =	$710.07		$774.4186	$774.42	$774.40	$774.40