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	$189.72	10.389%	$209.43	$209.43	$209.45	$209.40
Purchase #2	$101.51	5.793%	$107.3905	$107.39	$107.40	$107.40
Purchase #3	$167.77	6.871%	$179.2975	$179.30	$179.30	$179.30
Purchase #4	$219.34	6.443%	$233.4721	$233.47	$233.45	$233.50
Purchase #5	$34.35	5.471%	$36.2293	$36.23	$36.25	$36.20
Purchase #6	$193.41	11.844%	$216.3175	$216.32	$216.30	$216.30
Purchase #7	$39.29	10.168%	$43.285	$43.29	$43.30	$43.30
7 purchase totals =	$945.39		$1,025.4219	$1,025.43	$1,025.45	$1,025.40