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	$211.85	7.445%	$227.6222	$227.62	$227.60	$227.60
Purchase #2	$63.69	4.240%	$66.3905	$66.39	$66.40	$66.40
Purchase #3	$199.32	3.165%	$205.6285	$205.63	$205.65	$205.60
Purchase #4	$158.92	9.124%	$173.4199	$173.42	$173.40	$173.40
Purchase #5	$182.27	6.607%	$194.3126	$194.31	$194.30	$194.30
Purchase #6	$31.26	9.280%	$34.1609	$34.16	$34.15	$34.20
Purchase #7	$70.29	3.656%	$72.8598	$72.86	$72.85	$72.90
7 purchase totals =	$917.60		$974.3944	$974.39	$974.35	$974.40