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	$65.43	8.564%	$71.0334	$71.03	$71.05	$71.00
Purchase #2	$144.43	9.261%	$157.8057	$157.81	$157.80	$157.80
Purchase #3	$165.72	3.817%	$172.0455	$172.05	$172.05	$172.00
Purchase #4	$216.42	5.292%	$227.8729	$227.87	$227.85	$227.90
Purchase #5	$96.86	7.242%	$103.8746	$103.87	$103.85	$103.90
Purchase #6	$195.59	6.803%	$208.896	$208.90	$208.90	$208.90
Purchase #7	$189.42	8.549%	$205.6135	$205.61	$205.60	$205.60
7 purchase totals =	$1,073.87		$1,147.1416	$1,147.14	$1,147.10	$1,147.10