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	$140.39	5.187%	$147.672	$147.67	$147.65	$147.70
Purchase #2	$79.89	13.662%	$90.8046	$90.80	$90.80	$90.80
Purchase #3	$214.87	4.408%	$224.3415	$224.34	$224.35	$224.30
Purchase #4	$32.47	8.651%	$35.279	$35.28	$35.30	$35.30
Purchase #5	$172.60	8.676%	$187.5748	$187.57	$187.55	$187.60
Purchase #6	$249.96	13.802%	$284.4595	$284.46	$284.45	$284.50
Purchase #7	$37.54	6.861%	$40.1156	$40.12	$40.10	$40.10
7 purchase totals =	$927.72		$1,010.2470	$1,010.24	$1,010.20	$1,010.30