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	$168.38	13.282%	$190.7442	$190.74	$190.75	$190.70
Purchase #2	$69.81	3.557%	$72.2931	$72.29	$72.30	$72.30
Purchase #3	$12.92	10.800%	$14.3154	$14.32	$14.30	$14.30
Purchase #4	$185.31	13.534%	$210.3899	$210.39	$210.40	$210.40
Purchase #5	$97.34	11.798%	$108.8242	$108.82	$108.80	$108.80
Purchase #6	$177.96	4.267%	$185.5536	$185.55	$185.55	$185.60
Purchase #7	$47.39	8.180%	$51.2665	$51.27	$51.25	$51.30
7 purchase totals =	$759.11		$833.3869	$833.38	$833.35	$833.40