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	$67.61	4.782%	$70.8431	$70.84	$70.85	$70.80
Purchase #2	$13.40	4.537%	$14.008	$14.01	$14.00	$14.00
Purchase #3	$64.39	11.475%	$71.7788	$71.78	$71.80	$71.80
Purchase #4	$246.94	11.545%	$275.4492	$275.45	$275.45	$275.40
Purchase #5	$151.72	8.743%	$164.9849	$164.98	$165.00	$165.00
Purchase #6	$69.31	5.322%	$72.9987	$73.00	$73.00	$73.00
Purchase #7	$174.48	12.568%	$196.4086	$196.41	$196.40	$196.40
7 purchase totals =	$787.85		$866.4713	$866.47	$866.50	$866.40