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	$64.69	4.506%	$67.6049	$67.60	$67.60	$67.60
Purchase #2	$150.55	12.541%	$169.4305	$169.43	$169.45	$169.40
Purchase #3	$157.46	10.604%	$174.1571	$174.16	$174.15	$174.20
Purchase #4	$147.92	8.749%	$160.8615	$160.86	$160.85	$160.90
Purchase #5	$59.63	3.115%	$61.4875	$61.49	$61.50	$61.50
Purchase #6	$87.95	9.371%	$96.1918	$96.19	$96.20	$96.20
Purchase #7	$158.76	8.721%	$172.6055	$172.61	$172.60	$172.60
7 purchase totals =	$826.96		$902.3388	$902.34	$902.35	$902.40