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	$173.94	12.701%	$196.0321	$196.03	$196.05	$196.00
Purchase #2	$156.66	12.547%	$176.3161	$176.32	$176.30	$176.30
Purchase #3	$250.69	5.848%	$265.3504	$265.35	$265.35	$265.40
Purchase #4	$126.46	12.700%	$142.5204	$142.52	$142.50	$142.50
Purchase #5	$73.63	3.603%	$76.2829	$76.28	$76.30	$76.30
Purchase #6	$24.53	5.741%	$25.9383	$25.94	$25.95	$25.90
Purchase #7	$133.63	10.521%	$147.6892	$147.69	$147.70	$147.70
7 purchase totals =	$939.54		$1,030.1294	$1,030.13	$1,030.15	$1,030.10