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	$196.40	12.391%	$220.7359	$220.74	$220.75	$220.70
Purchase #2	$65.46	3.108%	$67.4945	$67.49	$67.50	$67.50
Purchase #3	$73.69	11.426%	$82.1098	$82.11	$82.10	$82.10
Purchase #4	$159.91	12.703%	$180.2234	$180.22	$180.20	$180.20
Purchase #5	$16.80	8.856%	$18.2878	$18.29	$18.30	$18.30
Purchase #6	$128.71	10.659%	$142.4292	$142.43	$142.45	$142.40
Purchase #7	$80.40	11.774%	$89.8663	$89.87	$89.85	$89.90
7 purchase totals =	$721.37		$801.1469	$801.15	$801.15	$801.10