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	$165.69	12.735%	$186.7906	$186.79	$186.80	$186.80
Purchase #2	$172.45	9.712%	$189.1983	$189.20	$189.20	$189.20
Purchase #3	$119.64	6.643%	$127.5877	$127.59	$127.60	$127.60
Purchase #4	$195.56	7.217%	$209.6736	$209.67	$209.65	$209.70
Purchase #5	$94.78	6.209%	$100.6649	$100.66	$100.65	$100.70
Purchase #6	$199.77	7.210%	$214.1734	$214.17	$214.15	$214.20
Purchase #7	$133.25	8.156%	$144.1179	$144.12	$144.10	$144.10
7 purchase totals =	$1,081.14		$1,172.2064	$1,172.20	$1,172.15	$1,172.30