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	$58.91	8.240%	$63.7642	$63.76	$63.75	$63.80
Purchase #2	$19.27	6.650%	$20.5515	$20.55	$20.55	$20.60
Purchase #3	$43.50	4.461%	$45.4405	$45.44	$45.45	$45.40
Purchase #4	$66.46	7.304%	$71.3142	$71.31	$71.30	$71.30
Purchase #5	$9.93	4.121%	$10.3392	$10.34	$10.35	$10.30
Purchase #6	$99.76	10.457%	$110.1919	$110.19	$110.20	$110.20
Purchase #7	$152.39	9.713%	$167.1916	$167.19	$167.20	$167.20
7 purchase totals =	$450.22		$488.7931	$488.78	$488.80	$488.80