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	$212.62	7.108%	$227.733	$227.73	$227.75	$227.70
Purchase #2	$134.77	6.577%	$143.6338	$143.63	$143.65	$143.60
Purchase #3	$30.38	8.264%	$32.8906	$32.89	$32.90	$32.90
Purchase #4	$219.73	8.753%	$238.963	$238.96	$238.95	$239.00
Purchase #5	$88.66	12.309%	$99.5732	$99.57	$99.55	$99.60
Purchase #6	$79.38	9.512%	$86.9306	$86.93	$86.95	$86.90
Purchase #7	$31.47	7.202%	$33.7365	$33.74	$33.75	$33.70
7 purchase totals =	$797.01		$863.4607	$863.45	$863.50	$863.40