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	$40.73	10.183%	$44.8775	$44.88	$44.90	$44.90
Purchase #2	$32.78	7.371%	$35.1962	$35.20	$35.20	$35.20
Purchase #3	$64.28	11.339%	$71.5687	$71.57	$71.55	$71.60
Purchase #4	$83.93	12.171%	$94.1451	$94.15	$94.15	$94.10
Purchase #5	$225.35	10.865%	$249.8343	$249.83	$249.85	$249.80
Purchase #6	$219.57	13.595%	$249.4205	$249.42	$249.40	$249.40
Purchase #7	$237.89	7.658%	$256.1076	$256.11	$256.10	$256.10
7 purchase totals =	$904.53		$1,001.1499	$1,001.16	$1,001.15	$1,001.10