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	$209.48	3.443%	$216.6924	$216.69	$216.70	$216.70
Purchase #2	$39.97	5.193%	$42.0456	$42.05	$42.05	$42.00
Purchase #3	$178.92	11.734%	$199.9145	$199.91	$199.90	$199.90
Purchase #4	$217.62	4.589%	$227.6066	$227.61	$227.60	$227.60
Purchase #5	$147.60	11.663%	$164.8146	$164.81	$164.80	$164.80
Purchase #6	$96.84	5.139%	$101.8166	$101.82	$101.80	$101.80
Purchase #7	$164.33	12.332%	$184.5952	$184.60	$184.60	$184.60
7 purchase totals =	$1,054.76		$1,137.4855	$1,137.49	$1,137.45	$1,137.40