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	$221.82	11.501%	$247.3315	$247.33	$247.35	$247.30
Purchase #2	$65.38	10.776%	$72.4253	$72.43	$72.45	$72.40
Purchase #3	$177.69	8.226%	$192.3068	$192.31	$192.30	$192.30
Purchase #4	$189.84	3.418%	$196.3287	$196.33	$196.35	$196.30
Purchase #5	$139.53	3.777%	$144.8	$144.80	$144.80	$144.80
Purchase #6	$124.64	11.167%	$138.5585	$138.56	$138.55	$138.60
Purchase #7	$47.29	6.841%	$50.5251	$50.53	$50.55	$50.50
7 purchase totals =	$966.19		$1,042.2759	$1,042.29	$1,042.35	$1,042.20