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	$152.80	9.669%	$167.5742	$167.57	$167.55	$167.60
Purchase #2	$88.46	4.504%	$92.4442	$92.44	$92.45	$92.40
Purchase #3	$91.33	10.659%	$101.0649	$101.06	$101.05	$101.10
Purchase #4	$233.51	9.616%	$255.9643	$255.96	$255.95	$256.00
Purchase #5	$175.26	9.565%	$192.0236	$192.02	$192.00	$192.00
Purchase #6	$80.30	11.305%	$89.3779	$89.38	$89.40	$89.40
Purchase #7	$147.35	12.594%	$165.9073	$165.91	$165.90	$165.90
7 purchase totals =	$969.01		$1,064.3564	$1,064.34	$1,064.30	$1,064.40