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	$44.73	12.772%	$50.4429	$50.44	$50.45	$50.40
Purchase #2	$239.45	13.166%	$270.976	$270.98	$271.00	$271.00
Purchase #3	$110.92	8.443%	$120.285	$120.29	$120.30	$120.30
Purchase #4	$31.90	6.108%	$33.8485	$33.85	$33.85	$33.80
Purchase #5	$92.69	8.515%	$100.5826	$100.58	$100.60	$100.60
Purchase #6	$234.69	10.127%	$258.4571	$258.46	$258.45	$258.50
Purchase #7	$55.25	12.484%	$62.1474	$62.15	$62.15	$62.10
7 purchase totals =	$809.63		$896.7395	$896.75	$896.80	$896.70