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	$65.70	5.818%	$69.5224	$69.52	$69.50	$69.50
Purchase #2	$192.82	8.104%	$208.4461	$208.45	$208.45	$208.40
Purchase #3	$214.33	11.262%	$238.4678	$238.47	$238.45	$238.50
Purchase #4	$180.41	13.871%	$205.4347	$205.43	$205.45	$205.40
Purchase #5	$49.61	5.394%	$52.286	$52.29	$52.30	$52.30
Purchase #6	$110.30	4.181%	$114.9116	$114.91	$114.90	$114.90
Purchase #7	$55.98	9.753%	$61.4397	$61.44	$61.45	$61.40
7 purchase totals =	$869.15		$950.5083	$950.51	$950.50	$950.40