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	$94.70	11.489%	$105.5801	$105.58	$105.60	$105.60
Purchase #2	$250.72	12.444%	$281.9196	$281.92	$281.90	$281.90
Purchase #3	$217.55	12.587%	$244.933	$244.93	$244.95	$244.90
Purchase #4	$156.30	9.151%	$170.603	$170.60	$170.60	$170.60
Purchase #5	$86.46	6.871%	$92.4007	$92.40	$92.40	$92.40
Purchase #6	$71.25	10.858%	$78.9863	$78.99	$79.00	$79.00
Purchase #7	$138.71	7.710%	$149.4045	$149.40	$149.40	$149.40
7 purchase totals =	$1,015.69		$1,123.8272	$1,123.82	$1,123.85	$1,123.80