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	$77.48	7.354%	$83.1779	$83.18	$83.20	$83.20
Purchase #2	$182.51	4.483%	$190.6919	$190.69	$190.70	$190.70
Purchase #3	$26.38	3.246%	$27.2363	$27.24	$27.25	$27.20
Purchase #4	$97.95	13.678%	$111.3476	$111.35	$111.35	$111.30
Purchase #5	$150.86	4.443%	$157.5627	$157.56	$157.55	$157.60
Purchase #6	$116.69	3.611%	$120.9037	$120.90	$120.90	$120.90
Purchase #7	$34.86	6.701%	$37.196	$37.20	$37.20	$37.20
7 purchase totals =	$686.73		$728.1161	$728.12	$728.15	$728.10