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	$59.50	10.674%	$65.851	$65.85	$65.85	$65.90
Purchase #2	$192.79	10.794%	$213.5998	$213.60	$213.60	$213.60
Purchase #3	$33.46	11.417%	$37.2801	$37.28	$37.30	$37.30
Purchase #4	$147.38	3.726%	$152.8714	$152.87	$152.85	$152.90
Purchase #5	$71.39	7.222%	$76.5458	$76.55	$76.55	$76.50
Purchase #6	$235.30	13.495%	$267.0537	$267.05	$267.05	$267.10
Purchase #7	$68.74	5.811%	$72.7345	$72.73	$72.75	$72.70
7 purchase totals =	$808.56		$885.9363	$885.93	$885.95	$886.00