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	$209.81	4.820%	$219.9228	$219.92	$219.90	$219.90
Purchase #2	$47.79	13.548%	$54.2646	$54.26	$54.25	$54.30
Purchase #3	$11.78	3.844%	$12.2328	$12.23	$12.25	$12.20
Purchase #4	$200.77	10.781%	$222.415	$222.42	$222.40	$222.40
Purchase #5	$243.61	13.678%	$276.931	$276.93	$276.95	$276.90
Purchase #6	$219.98	12.329%	$247.1013	$247.10	$247.10	$247.10
Purchase #7	$142.48	9.697%	$156.2963	$156.30	$156.30	$156.30
7 purchase totals =	$1,076.22		$1,189.1638	$1,189.16	$1,189.15	$1,189.10