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	$105.41	4.252%	$109.892	$109.89	$109.90	$109.90
Purchase #2	$76.93	7.342%	$82.5782	$82.58	$82.60	$82.60
Purchase #3	$70.26	7.431%	$75.481	$75.48	$75.50	$75.50
Purchase #4	$209.93	11.722%	$234.538	$234.54	$234.55	$234.50
Purchase #5	$108.34	7.588%	$116.5608	$116.56	$116.55	$116.60
Purchase #6	$172.69	6.657%	$184.186	$184.19	$184.20	$184.20
Purchase #7	$110.54	7.264%	$118.5696	$118.57	$118.55	$118.60
7 purchase totals =	$854.10		$921.8056	$921.81	$921.85	$921.90