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	$200.83	7.361%	$215.6131	$215.61	$215.60	$215.60
Purchase #2	$219.66	11.267%	$244.4091	$244.41	$244.40	$244.40
Purchase #3	$80.86	8.762%	$87.945	$87.95	$87.95	$87.90
Purchase #4	$158.81	8.619%	$172.4978	$172.50	$172.50	$172.50
Purchase #5	$229.34	7.498%	$246.5359	$246.54	$246.55	$246.50
Purchase #6	$109.98	9.227%	$120.1279	$120.13	$120.15	$120.10
Purchase #7	$83.48	6.721%	$89.0907	$89.09	$89.10	$89.10
7 purchase totals =	$1,082.96		$1,176.2195	$1,176.23	$1,176.25	$1,176.10