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	$169.61	11.609%	$189.3	$189.30	$189.30	$189.30
Purchase #2	$172.33	11.600%	$192.3203	$192.32	$192.30	$192.30
Purchase #3	$141.70	5.256%	$149.1478	$149.15	$149.15	$149.10
Purchase #4	$230.77	10.734%	$255.5409	$255.54	$255.55	$255.50
Purchase #5	$223.32	5.107%	$234.725	$234.73	$234.75	$234.70
Purchase #6	$115.79	13.769%	$131.7331	$131.73	$131.75	$131.70
Purchase #7	$154.89	4.444%	$161.7733	$161.77	$161.75	$161.80
7 purchase totals =	$1,208.41		$1,314.5404	$1,314.54	$1,314.55	$1,314.40