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	$210.38	4.216%	$219.2496	$219.25	$219.25	$219.20
Purchase #2	$180.54	4.788%	$189.1843	$189.18	$189.20	$189.20
Purchase #3	$97.80	10.766%	$108.3291	$108.33	$108.35	$108.30
Purchase #4	$200.38	12.222%	$224.8704	$224.87	$224.85	$224.90
Purchase #5	$43.85	3.736%	$45.4882	$45.49	$45.50	$45.50
Purchase #6	$174.50	6.644%	$186.0938	$186.09	$186.10	$186.10
Purchase #7	$77.81	6.850%	$83.14	$83.14	$83.15	$83.10
7 purchase totals =	$985.26		$1,056.3554	$1,056.35	$1,056.40	$1,056.30