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	$192.49	6.452%	$204.9095	$204.91	$204.90	$204.90
Purchase #2	$220.38	10.189%	$242.8345	$242.83	$242.85	$242.80
Purchase #3	$184.84	6.501%	$196.8564	$196.86	$196.85	$196.90
Purchase #4	$124.79	5.369%	$131.49	$131.49	$131.50	$131.50
Purchase #5	$139.70	5.353%	$147.1781	$147.18	$147.20	$147.20
Purchase #6	$147.54	12.608%	$166.1418	$166.14	$166.15	$166.10
Purchase #7	$223.49	8.212%	$241.843	$241.84	$241.85	$241.80
7 purchase totals =	$1,233.23		$1,331.2533	$1,331.25	$1,331.30	$1,331.20