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	$113.29	10.300%	$124.9589	$124.96	$124.95	$125.00
Purchase #2	$122.86	3.702%	$127.4083	$127.41	$127.40	$127.40
Purchase #3	$62.60	13.556%	$71.0861	$71.09	$71.10	$71.10
Purchase #4	$85.41	11.401%	$95.1476	$95.15	$95.15	$95.10
Purchase #5	$229.92	3.136%	$237.1303	$237.13	$237.15	$237.10
Purchase #6	$65.60	8.133%	$70.9352	$70.94	$70.95	$70.90
Purchase #7	$81.84	8.596%	$88.875	$88.88	$88.90	$88.90
7 purchase totals =	$761.52		$815.5414	$815.56	$815.60	$815.50