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	$142.97	5.739%	$151.175	$151.18	$151.20	$151.20
Purchase #2	$52.50	6.506%	$55.9157	$55.92	$55.90	$55.90
Purchase #3	$213.75	10.141%	$235.4264	$235.43	$235.45	$235.40
Purchase #4	$103.88	12.389%	$116.7497	$116.75	$116.75	$116.70
Purchase #5	$250.78	8.595%	$272.3345	$272.33	$272.35	$272.30
Purchase #6	$90.46	12.541%	$101.8046	$101.80	$101.80	$101.80
Purchase #7	$120.44	5.487%	$127.0485	$127.05	$127.05	$127.00
7 purchase totals =	$974.78		$1,060.4544	$1,060.46	$1,060.50	$1,060.30