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	$118.38	4.570%	$123.79	$123.79	$123.80	$123.80
Purchase #2	$93.49	5.316%	$98.4599	$98.46	$98.45	$98.50
Purchase #3	$224.71	7.567%	$241.7138	$241.71	$241.70	$241.70
Purchase #4	$47.72	8.653%	$51.8492	$51.85	$51.85	$51.80
Purchase #5	$129.53	10.231%	$142.7822	$142.78	$142.80	$142.80
Purchase #6	$90.40	10.487%	$99.8802	$99.88	$99.90	$99.90
Purchase #7	$129.71	6.274%	$137.848	$137.85	$137.85	$137.80
7 purchase totals =	$833.94		$896.3233	$896.32	$896.35	$896.30