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	$78.33	5.251%	$82.4431	$82.44	$82.45	$82.40
Purchase #2	$32.95	12.676%	$37.1267	$37.13	$37.15	$37.10
Purchase #3	$219.89	7.378%	$236.1135	$236.11	$236.10	$236.10
Purchase #4	$207.83	7.184%	$222.7605	$222.76	$222.75	$222.80
Purchase #5	$164.39	8.570%	$178.4782	$178.48	$178.50	$178.50
Purchase #6	$146.50	13.543%	$166.3405	$166.34	$166.35	$166.30
Purchase #7	$226.71	13.630%	$257.6106	$257.61	$257.60	$257.60
7 purchase totals =	$1,076.60		$1,180.8731	$1,180.87	$1,180.90	$1,180.80