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	$176.50	11.519%	$196.831	$196.83	$196.85	$196.80
Purchase #2	$203.27	11.557%	$226.7619	$226.76	$226.75	$226.80
Purchase #3	$32.39	8.778%	$35.2332	$35.23	$35.25	$35.20
Purchase #4	$139.80	5.538%	$147.5421	$147.54	$147.55	$147.50
Purchase #5	$22.37	10.567%	$24.7338	$24.73	$24.75	$24.70
Purchase #6	$224.93	11.432%	$250.644	$250.64	$250.65	$250.60
Purchase #7	$90.78	9.728%	$99.6111	$99.61	$99.60	$99.60
7 purchase totals =	$890.04		$981.3571	$981.34	$981.40	$981.20