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	$73.50	6.373%	$78.1842	$78.18	$78.20	$78.20
Purchase #2	$33.34	11.196%	$37.0727	$37.07	$37.05	$37.10
Purchase #3	$218.83	8.846%	$238.1877	$238.19	$238.20	$238.20
Purchase #4	$205.31	9.613%	$225.0465	$225.05	$225.05	$225.00
Purchase #5	$147.33	7.181%	$157.9098	$157.91	$157.90	$157.90
Purchase #6	$178.87	7.555%	$192.3836	$192.38	$192.40	$192.40
Purchase #7	$80.92	5.809%	$85.6206	$85.62	$85.60	$85.60
7 purchase totals =	$938.10		$1,014.4051	$1,014.40	$1,014.40	$1,014.40