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	$148.67	7.141%	$159.2865	$159.29	$159.30	$159.30
Purchase #2	$190.99	12.256%	$214.3977	$214.40	$214.40	$214.40
Purchase #3	$63.69	12.870%	$71.8869	$71.89	$71.90	$71.90
Purchase #4	$114.88	7.292%	$123.257	$123.26	$123.25	$123.30
Purchase #5	$47.98	9.470%	$52.5237	$52.52	$52.50	$52.50
Purchase #6	$218.56	11.385%	$243.4431	$243.44	$243.45	$243.40
Purchase #7	$10.59	10.350%	$11.6861	$11.69	$11.70	$11.70
7 purchase totals =	$795.36		$876.4810	$876.49	$876.50	$876.50