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	$196.30	12.250%	$220.3468	$220.35	$220.35	$220.30
Purchase #2	$177.46	4.338%	$185.1582	$185.16	$185.15	$185.20
Purchase #3	$148.38	8.168%	$160.4997	$160.50	$160.50	$160.50
Purchase #4	$89.82	3.111%	$92.6143	$92.61	$92.60	$92.60
Purchase #5	$108.33	8.740%	$117.798	$117.80	$117.80	$117.80
Purchase #6	$109.95	7.669%	$118.3821	$118.38	$118.40	$118.40
Purchase #7	$82.67	9.703%	$90.6915	$90.69	$90.70	$90.70
7 purchase totals =	$912.91		$985.4906	$985.49	$985.50	$985.50