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	$145.47	4.541%	$152.0758	$152.08	$152.10	$152.10
Purchase #2	$239.77	6.131%	$254.4703	$254.47	$254.45	$254.50
Purchase #3	$139.96	11.585%	$156.1744	$156.17	$156.15	$156.20
Purchase #4	$163.60	4.746%	$171.3645	$171.36	$171.35	$171.40
Purchase #5	$200.79	10.288%	$221.4473	$221.45	$221.45	$221.40
Purchase #6	$100.61	13.706%	$114.3996	$114.40	$114.40	$114.40
Purchase #7	$65.69	9.785%	$72.1178	$72.12	$72.10	$72.10
7 purchase totals =	$1,055.89		$1,142.0497	$1,142.05	$1,142.00	$1,142.10