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	$64.83	4.236%	$67.5762	$67.58	$67.60	$67.60
Purchase #2	$218.43	9.385%	$238.9297	$238.93	$238.95	$238.90
Purchase #3	$160.98	11.289%	$179.153	$179.15	$179.15	$179.20
Purchase #4	$185.64	5.172%	$195.2413	$195.24	$195.25	$195.20
Purchase #5	$162.83	13.561%	$184.9114	$184.91	$184.90	$184.90
Purchase #6	$95.85	8.660%	$104.1506	$104.15	$104.15	$104.20
Purchase #7	$169.84	12.133%	$190.4467	$190.45	$190.45	$190.40
7 purchase totals =	$1,058.40		$1,160.4089	$1,160.41	$1,160.45	$1,160.40