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	$212.94	3.155%	$219.6583	$219.66	$219.65	$219.70
Purchase #2	$33.51	10.823%	$37.1368	$37.14	$37.15	$37.10
Purchase #3	$78.79	4.756%	$82.5373	$82.54	$82.55	$82.50
Purchase #4	$75.99	3.362%	$78.5448	$78.54	$78.55	$78.50
Purchase #5	$24.35	12.144%	$27.3071	$27.31	$27.30	$27.30
Purchase #6	$243.78	11.822%	$272.5997	$272.60	$272.60	$272.60
Purchase #7	$96.76	12.263%	$108.6257	$108.63	$108.65	$108.60
7 purchase totals =	$766.12		$826.4097	$826.42	$826.45	$826.30