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	$78.91	4.743%	$82.6527	$82.65	$82.65	$82.70
Purchase #2	$97.97	5.794%	$103.6464	$103.65	$103.65	$103.60
Purchase #3	$199.59	11.531%	$222.6047	$222.60	$222.60	$222.60
Purchase #4	$40.84	6.324%	$43.4227	$43.42	$43.40	$43.40
Purchase #5	$81.72	5.424%	$86.1525	$86.15	$86.15	$86.20
Purchase #6	$77.99	7.494%	$83.8346	$83.83	$83.85	$83.80
Purchase #7	$241.35	13.453%	$273.8188	$273.82	$273.80	$273.80
7 purchase totals =	$818.37		$896.1324	$896.12	$896.10	$896.10