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	$199.92	5.601%	$211.1175	$211.12	$211.10	$211.10
Purchase #2	$151.38	12.839%	$170.8157	$170.82	$170.80	$170.80
Purchase #3	$222.40	11.721%	$248.4675	$248.47	$248.45	$248.50
Purchase #4	$35.88	12.229%	$40.2678	$40.27	$40.25	$40.30
Purchase #5	$80.50	3.773%	$83.5373	$83.54	$83.55	$83.50
Purchase #6	$164.70	10.311%	$181.6822	$181.68	$181.70	$181.70
Purchase #7	$192.39	8.359%	$208.4719	$208.47	$208.45	$208.50
7 purchase totals =	$1,047.17		$1,144.3599	$1,144.37	$1,144.30	$1,144.40