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	$109.74	5.103%	$115.34	$115.34	$115.35	$115.30
Purchase #2	$8.29	7.107%	$8.8792	$8.88	$8.90	$8.90
Purchase #3	$94.41	5.823%	$99.9075	$99.91	$99.90	$99.90
Purchase #4	$126.58	10.186%	$139.4734	$139.47	$139.45	$139.50
Purchase #5	$100.79	10.646%	$111.5201	$111.52	$111.50	$111.50
Purchase #6	$117.77	7.202%	$126.2518	$126.25	$126.25	$126.30
Purchase #7	$209.47	4.206%	$218.2803	$218.28	$218.30	$218.30
7 purchase totals =	$767.05		$819.6523	$819.65	$819.65	$819.70