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	$31.46	9.169%	$34.3446	$34.34	$34.35	$34.30
Purchase #2	$145.67	11.602%	$162.5706	$162.57	$162.55	$162.60
Purchase #3	$71.84	8.718%	$78.103	$78.10	$78.10	$78.10
Purchase #4	$50.60	8.532%	$54.9172	$54.92	$54.90	$54.90
Purchase #5	$91.43	5.612%	$96.5611	$96.56	$96.55	$96.60
Purchase #6	$153.39	8.664%	$166.6797	$166.68	$166.70	$166.70
Purchase #7	$79.56	3.372%	$82.2428	$82.24	$82.25	$82.20
7 purchase totals =	$623.95		$675.4190	$675.41	$675.40	$675.40