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	$212.92	12.442%	$239.4115	$239.41	$239.40	$239.40
Purchase #2	$7.60	12.105%	$8.52	$8.52	$8.50	$8.50
Purchase #3	$230.26	12.617%	$259.3119	$259.31	$259.30	$259.30
Purchase #4	$214.79	13.709%	$244.2356	$244.24	$244.25	$244.20
Purchase #5	$140.37	5.263%	$147.7577	$147.76	$147.75	$147.80
Purchase #6	$65.82	7.872%	$71.0014	$71.00	$71.00	$71.00
Purchase #7	$184.31	6.585%	$196.4468	$196.45	$196.45	$196.40
7 purchase totals =	$1,056.07		$1,166.6849	$1,166.69	$1,166.65	$1,166.60