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	$34.70	8.548%	$37.6662	$37.67	$37.65	$37.70
Purchase #2	$105.25	8.602%	$114.3036	$114.30	$114.30	$114.30
Purchase #3	$64.98	11.777%	$72.6327	$72.63	$72.65	$72.60
Purchase #4	$38.54	11.348%	$42.9135	$42.91	$42.90	$42.90
Purchase #5	$136.33	5.365%	$143.6441	$143.64	$143.65	$143.60
Purchase #6	$105.82	6.235%	$112.4179	$112.42	$112.40	$112.40
Purchase #7	$111.31	7.873%	$120.0734	$120.07	$120.05	$120.10
7 purchase totals =	$596.93		$643.6514	$643.64	$643.60	$643.60