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	$195.93	12.494%	$220.4095	$220.41	$220.40	$220.40
Purchase #2	$26.61	3.255%	$27.4762	$27.48	$27.50	$27.50
Purchase #3	$52.89	8.514%	$57.3931	$57.39	$57.40	$57.40
Purchase #4	$94.27	3.860%	$97.9088	$97.91	$97.90	$97.90
Purchase #5	$82.86	3.162%	$85.48	$85.48	$85.50	$85.50
Purchase #6	$183.38	4.795%	$192.1731	$192.17	$192.15	$192.20
Purchase #7	$179.40	11.760%	$200.4974	$200.50	$200.50	$200.50
7 purchase totals =	$815.34		$881.3381	$881.34	$881.35	$881.40