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	$151.75	3.769%	$157.4695	$157.47	$157.45	$157.50
Purchase #2	$57.55	12.554%	$64.7748	$64.77	$64.75	$64.80
Purchase #3	$175.73	11.467%	$195.881	$195.88	$195.90	$195.90
Purchase #4	$240.98	7.241%	$258.4294	$258.43	$258.45	$258.40
Purchase #5	$72.84	11.853%	$81.4737	$81.47	$81.45	$81.50
Purchase #6	$119.46	9.677%	$131.0201	$131.02	$131.00	$131.00
Purchase #7	$199.31	5.580%	$210.4315	$210.43	$210.45	$210.40
7 purchase totals =	$1,017.62		$1,099.4800	$1,099.47	$1,099.45	$1,099.50