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	$149.60	11.804%	$167.2588	$167.26	$167.25	$167.30
Purchase #2	$134.38	13.351%	$152.3211	$152.32	$152.30	$152.30
Purchase #3	$32.99	12.199%	$37.0145	$37.01	$37.00	$37.00
Purchase #4	$70.54	9.593%	$77.3069	$77.31	$77.30	$77.30
Purchase #5	$192.41	10.210%	$212.0551	$212.06	$212.05	$212.10
Purchase #6	$65.83	10.570%	$72.7882	$72.79	$72.80	$72.80
Purchase #7	$82.61	9.515%	$90.4703	$90.47	$90.45	$90.50
7 purchase totals =	$728.36		$809.2149	$809.22	$809.15	$809.30