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	$210.39	13.143%	$238.0416	$238.04	$238.05	$238.00
Purchase #2	$83.54	6.596%	$89.0503	$89.05	$89.05	$89.10
Purchase #3	$41.58	12.607%	$46.822	$46.82	$46.80	$46.80
Purchase #4	$200.42	3.271%	$206.9757	$206.98	$207.00	$207.00
Purchase #5	$92.98	11.446%	$103.6225	$103.62	$103.60	$103.60
Purchase #6	$61.50	12.327%	$69.0811	$69.08	$69.10	$69.10
Purchase #7	$67.65	5.716%	$71.5169	$71.52	$71.50	$71.50
7 purchase totals =	$758.06		$825.1101	$825.11	$825.10	$825.10