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	$103.98	7.570%	$111.8513	$111.85	$111.85	$111.90
Purchase #2	$211.38	5.457%	$222.915	$222.92	$222.90	$222.90
Purchase #3	$125.57	7.203%	$134.6148	$134.61	$134.60	$134.60
Purchase #4	$229.83	6.779%	$245.4102	$245.41	$245.40	$245.40
Purchase #5	$171.47	4.602%	$179.361	$179.36	$179.35	$179.40
Purchase #6	$134.86	9.242%	$147.3238	$147.32	$147.30	$147.30
Purchase #7	$140.48	5.313%	$147.9437	$147.94	$147.95	$147.90
7 purchase totals =	$1,117.57		$1,189.4198	$1,189.41	$1,189.35	$1,189.40