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	$112.77	5.180%	$118.6115	$118.61	$118.60	$118.60
Purchase #2	$147.43	3.281%	$152.2672	$152.27	$152.25	$152.30
Purchase #3	$105.78	11.703%	$118.1594	$118.16	$118.15	$118.20
Purchase #4	$178.53	7.296%	$191.5555	$191.56	$191.55	$191.60
Purchase #5	$171.37	12.356%	$192.5445	$192.54	$192.55	$192.50
Purchase #6	$150.37	12.238%	$168.7723	$168.77	$168.75	$168.80
Purchase #7	$217.69	9.713%	$238.8342	$238.83	$238.85	$238.80
7 purchase totals =	$1,083.94		$1,180.7446	$1,180.74	$1,180.70	$1,180.80