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	$215.83	10.321%	$238.1058	$238.11	$238.10	$238.10
Purchase #2	$27.51	3.559%	$28.4891	$28.49	$28.50	$28.50
Purchase #3	$76.64	5.495%	$80.8514	$80.85	$80.85	$80.90
Purchase #4	$154.66	9.216%	$168.9135	$168.91	$168.90	$168.90
Purchase #5	$151.42	10.827%	$167.8142	$167.81	$167.80	$167.80
Purchase #6	$162.95	11.769%	$182.1276	$182.13	$182.15	$182.10
Purchase #7	$185.29	8.734%	$201.4732	$201.47	$201.45	$201.50
7 purchase totals =	$974.30		$1,067.7748	$1,067.77	$1,067.75	$1,067.80