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	$197.88	11.532%	$220.6995	$220.70	$220.70	$220.70
Purchase #2	$117.59	4.726%	$123.1473	$123.15	$123.15	$123.10
Purchase #3	$55.88	13.837%	$63.6121	$63.61	$63.60	$63.60
Purchase #4	$152.49	6.614%	$162.5757	$162.58	$162.60	$162.60
Purchase #5	$32.91	9.127%	$35.9137	$35.91	$35.90	$35.90
Purchase #6	$248.87	13.258%	$281.8652	$281.87	$281.85	$281.90
Purchase #7	$233.83	4.490%	$244.329	$244.33	$244.35	$244.30
7 purchase totals =	$1,039.45		$1,132.1425	$1,132.15	$1,132.15	$1,132.10