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	$70.65	4.242%	$73.647	$73.65	$73.65	$73.60
Purchase #2	$33.63	12.463%	$37.8213	$37.82	$37.80	$37.80
Purchase #3	$36.73	5.744%	$38.8398	$38.84	$38.85	$38.80
Purchase #4	$67.60	7.218%	$72.4794	$72.48	$72.50	$72.50
Purchase #5	$97.35	13.464%	$110.4572	$110.46	$110.45	$110.50
Purchase #6	$237.51	9.597%	$260.3038	$260.30	$260.30	$260.30
Purchase #7	$83.72	13.846%	$95.3119	$95.31	$95.30	$95.30
7 purchase totals =	$627.19		$688.8604	$688.86	$688.85	$688.80