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	$63.73	12.649%	$71.7912	$71.79	$71.80	$71.80
Purchase #2	$165.81	11.803%	$185.3806	$185.38	$185.40	$185.40
Purchase #3	$75.51	4.421%	$78.8483	$78.85	$78.85	$78.80
Purchase #4	$224.32	8.568%	$243.5397	$243.54	$243.55	$243.50
Purchase #5	$161.72	6.586%	$172.3709	$172.37	$172.35	$172.40
Purchase #6	$152.78	7.594%	$164.3821	$164.38	$164.40	$164.40
Purchase #7	$136.29	7.432%	$146.4191	$146.42	$146.40	$146.40
7 purchase totals =	$980.16		$1,062.7319	$1,062.73	$1,062.75	$1,062.70