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	$217.64	9.374%	$238.0416	$238.04	$238.05	$238.00
Purchase #2	$151.96	13.521%	$172.5065	$172.51	$172.50	$172.50
Purchase #3	$37.56	4.711%	$39.3295	$39.33	$39.35	$39.30
Purchase #4	$80.72	11.422%	$89.9398	$89.94	$89.95	$89.90
Purchase #5	$120.63	4.731%	$126.337	$126.34	$126.35	$126.30
Purchase #6	$92.76	9.320%	$101.4052	$101.41	$101.40	$101.40
Purchase #7	$112.51	8.226%	$121.7651	$121.77	$121.75	$121.80
7 purchase totals =	$813.78		$889.3247	$889.34	$889.35	$889.20