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	$142.99	10.117%	$157.4563	$157.46	$157.45	$157.50
Purchase #2	$141.74	9.288%	$154.9048	$154.90	$154.90	$154.90
Purchase #3	$168.97	9.813%	$185.551	$185.55	$185.55	$185.60
Purchase #4	$20.91	9.279%	$22.8502	$22.85	$22.85	$22.90
Purchase #5	$175.35	8.628%	$190.4792	$190.48	$190.50	$190.50
Purchase #6	$190.60	12.494%	$214.4136	$214.41	$214.40	$214.40
Purchase #7	$76.30	12.482%	$85.8238	$85.82	$85.80	$85.80
7 purchase totals =	$916.86		$1,011.4789	$1,011.47	$1,011.45	$1,011.60