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	$44.53	13.735%	$50.6462	$50.65	$50.65	$50.60
Purchase #2	$100.79	4.153%	$104.9758	$104.98	$105.00	$105.00
Purchase #3	$98.54	4.477%	$102.9516	$102.95	$102.95	$103.00
Purchase #4	$101.62	9.229%	$110.9985	$111.00	$111.00	$111.00
Purchase #5	$67.53	3.503%	$69.8956	$69.90	$69.90	$69.90
Purchase #6	$127.42	4.679%	$133.382	$133.38	$133.40	$133.40
Purchase #7	$118.68	7.412%	$127.4766	$127.48	$127.50	$127.50
7 purchase totals =	$659.11		$700.3263	$700.34	$700.40	$700.40