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	$176.97	5.187%	$186.1494	$186.15	$186.15	$186.10
Purchase #2	$151.53	13.821%	$172.473	$172.47	$172.45	$172.50
Purchase #3	$9.28	13.533%	$10.5359	$10.54	$10.55	$10.50
Purchase #4	$232.56	7.665%	$250.3857	$250.39	$250.40	$250.40
Purchase #5	$58.88	8.721%	$64.0149	$64.01	$64.00	$64.00
Purchase #6	$155.42	7.529%	$167.1216	$167.12	$167.10	$167.10
Purchase #7	$148.86	13.318%	$168.6852	$168.69	$168.70	$168.70
7 purchase totals =	$933.50		$1,019.3657	$1,019.37	$1,019.35	$1,019.30