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	$61.76	9.394%	$67.5617	$67.56	$67.55	$67.60
Purchase #2	$129.69	9.611%	$142.1545	$142.15	$142.15	$142.20
Purchase #3	$236.94	10.363%	$261.4941	$261.49	$261.50	$261.50
Purchase #4	$150.39	5.136%	$158.114	$158.11	$158.10	$158.10
Purchase #5	$127.92	11.557%	$142.7037	$142.70	$142.70	$142.70
Purchase #6	$243.95	4.735%	$255.501	$255.50	$255.50	$255.50
Purchase #7	$186.44	9.598%	$204.3345	$204.33	$204.35	$204.30
7 purchase totals =	$1,137.09		$1,231.8635	$1,231.84	$1,231.85	$1,231.90