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	$162.52	3.306%	$167.8929	$167.89	$167.90	$167.90
Purchase #2	$178.39	5.530%	$188.255	$188.26	$188.25	$188.30
Purchase #3	$100.75	8.758%	$109.5737	$109.57	$109.55	$109.60
Purchase #4	$100.36	4.640%	$105.0167	$105.02	$105.00	$105.00
Purchase #5	$156.40	11.411%	$174.2468	$174.25	$174.25	$174.20
Purchase #6	$11.51	9.276%	$12.5777	$12.58	$12.60	$12.60
Purchase #7	$148.95	13.114%	$168.4833	$168.48	$168.50	$168.50
7 purchase totals =	$858.88		$926.0461	$926.05	$926.05	$926.10