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	$148.44	13.620%	$168.6575	$168.66	$168.65	$168.70
Purchase #2	$35.89	3.659%	$37.2032	$37.20	$37.20	$37.20
Purchase #3	$141.46	9.290%	$154.6016	$154.60	$154.60	$154.60
Purchase #4	$54.50	9.810%	$59.8465	$59.85	$59.85	$59.80
Purchase #5	$174.57	6.811%	$186.46	$186.46	$186.45	$186.50
Purchase #6	$134.27	9.873%	$147.5265	$147.53	$147.55	$147.50
Purchase #7	$75.75	5.159%	$79.6579	$79.66	$79.65	$79.70
7 purchase totals =	$764.88		$833.9532	$833.96	$833.95	$834.00