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	$105.89	7.555%	$113.89	$113.89	$113.90	$113.90
Purchase #2	$92.52	5.290%	$97.4143	$97.41	$97.40	$97.40
Purchase #3	$154.43	12.353%	$173.5067	$173.51	$173.50	$173.50
Purchase #4	$139.66	9.161%	$152.4543	$152.45	$152.45	$152.50
Purchase #5	$105.54	4.465%	$110.2524	$110.25	$110.25	$110.30
Purchase #6	$52.89	12.382%	$59.4388	$59.44	$59.45	$59.40
Purchase #7	$38.36	7.641%	$41.2911	$41.29	$41.30	$41.30
7 purchase totals =	$689.29		$748.2476	$748.24	$748.25	$748.30