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	$35.35	5.214%	$37.1931	$37.19	$37.20	$37.20
Purchase #2	$193.69	11.318%	$215.6118	$215.61	$215.60	$215.60
Purchase #3	$78.60	8.562%	$85.3297	$85.33	$85.35	$85.30
Purchase #4	$17.62	5.641%	$18.6139	$18.61	$18.60	$18.60
Purchase #5	$160.55	8.358%	$173.9688	$173.97	$173.95	$174.00
Purchase #6	$172.97	6.449%	$184.1248	$184.12	$184.10	$184.10
Purchase #7	$167.92	10.555%	$185.644	$185.64	$185.65	$185.60
7 purchase totals =	$826.70		$900.4861	$900.47	$900.45	$900.40