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	$170.29	8.629%	$184.9843	$184.98	$185.00	$185.00
Purchase #2	$200.57	7.744%	$216.1021	$216.10	$216.10	$216.10
Purchase #3	$24.65	13.138%	$27.8885	$27.89	$27.90	$27.90
Purchase #4	$226.92	12.748%	$255.8478	$255.85	$255.85	$255.80
Purchase #5	$111.39	6.181%	$118.275	$118.28	$118.30	$118.30
Purchase #6	$139.79	8.198%	$151.25	$151.25	$151.25	$151.30
Purchase #7	$88.97	3.124%	$91.7494	$91.75	$91.75	$91.70
7 purchase totals =	$962.58		$1,046.0971	$1,046.10	$1,046.15	$1,046.10