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	$215.72	3.553%	$223.3845	$223.38	$223.40	$223.40
Purchase #2	$240.77	11.487%	$268.4272	$268.43	$268.45	$268.40
Purchase #3	$217.38	8.482%	$235.8182	$235.82	$235.80	$235.80
Purchase #4	$164.98	8.465%	$178.9456	$178.95	$178.95	$178.90
Purchase #5	$181.45	10.408%	$200.3353	$200.34	$200.35	$200.30
Purchase #6	$219.49	9.830%	$241.0659	$241.07	$241.05	$241.10
Purchase #7	$30.56	6.226%	$32.4627	$32.46	$32.45	$32.50
7 purchase totals =	$1,270.35		$1,380.4394	$1,380.45	$1,380.45	$1,380.40