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	$244.88	13.344%	$277.5568	$277.56	$277.55	$277.60
Purchase #2	$82.90	7.356%	$88.9981	$89.00	$89.00	$89.00
Purchase #3	$182.85	7.381%	$196.3462	$196.35	$196.35	$196.30
Purchase #4	$204.73	8.798%	$222.7421	$222.74	$222.75	$222.70
Purchase #5	$69.70	4.251%	$72.6629	$72.66	$72.65	$72.70
Purchase #6	$52.45	13.723%	$59.6477	$59.65	$59.65	$59.60
Purchase #7	$113.50	7.502%	$122.0148	$122.01	$122.00	$122.00
7 purchase totals =	$951.01		$1,039.9686	$1,039.97	$1,039.95	$1,039.90