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	$205.90	8.535%	$223.4736	$223.47	$223.45	$223.50
Purchase #2	$130.75	7.613%	$140.704	$140.70	$140.70	$140.70
Purchase #3	$156.83	5.452%	$165.3804	$165.38	$165.40	$165.40
Purchase #4	$151.58	8.690%	$164.7523	$164.75	$164.75	$164.80
Purchase #5	$241.53	4.804%	$253.1331	$253.13	$253.15	$253.10
Purchase #6	$164.85	4.755%	$172.6886	$172.69	$172.70	$172.70
Purchase #7	$146.60	10.870%	$162.5354	$162.54	$162.55	$162.50
7 purchase totals =	$1,198.04		$1,282.6674	$1,282.66	$1,282.70	$1,282.70