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	$197.83	10.647%	$218.893	$218.89	$218.90	$218.90
Purchase #2	$220.92	13.492%	$250.7265	$250.73	$250.75	$250.70
Purchase #3	$136.58	3.249%	$141.0175	$141.02	$141.00	$141.00
Purchase #4	$159.50	8.347%	$172.8135	$172.81	$172.80	$172.80
Purchase #5	$219.91	3.584%	$227.7916	$227.79	$227.80	$227.80
Purchase #6	$69.96	10.519%	$77.3191	$77.32	$77.30	$77.30
Purchase #7	$119.45	3.324%	$123.4205	$123.42	$123.40	$123.40
7 purchase totals =	$1,124.15		$1,211.9817	$1,211.98	$1,211.95	$1,211.90