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	$238.42	11.868%	$266.7157	$266.72	$266.70	$266.70
Purchase #2	$73.40	5.322%	$77.3063	$77.31	$77.30	$77.30
Purchase #3	$69.49	12.650%	$78.2805	$78.28	$78.30	$78.30
Purchase #4	$84.97	7.191%	$91.0802	$91.08	$91.10	$91.10
Purchase #5	$81.50	13.696%	$92.6622	$92.66	$92.65	$92.70
Purchase #6	$144.97	11.855%	$162.1562	$162.16	$162.15	$162.20
Purchase #7	$151.58	13.458%	$171.9796	$171.98	$172.00	$172.00
7 purchase totals =	$844.33		$940.1807	$940.19	$940.20	$940.30