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	$199.78	5.227%	$210.2225	$210.22	$210.20	$210.20
Purchase #2	$57.43	3.568%	$59.4791	$59.48	$59.50	$59.50
Purchase #3	$212.56	3.164%	$219.2854	$219.29	$219.30	$219.30
Purchase #4	$83.47	4.581%	$87.2938	$87.29	$87.30	$87.30
Purchase #5	$136.61	3.109%	$140.8572	$140.86	$140.85	$140.90
Purchase #6	$229.27	13.808%	$260.9276	$260.93	$260.95	$260.90
Purchase #7	$105.72	9.589%	$115.8575	$115.86	$115.85	$115.90
7 purchase totals =	$1,024.84		$1,093.9231	$1,093.93	$1,093.95	$1,094.00