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	$84.70	11.569%	$94.4989	$94.50	$94.50	$94.50
Purchase #2	$189.66	3.413%	$196.1331	$196.13	$196.15	$196.10
Purchase #3	$52.98	3.173%	$54.6611	$54.66	$54.65	$54.70
Purchase #4	$42.56	7.264%	$45.6516	$45.65	$45.65	$45.70
Purchase #5	$79.52	9.215%	$86.8478	$86.85	$86.85	$86.80
Purchase #6	$241.53	11.478%	$269.2528	$269.25	$269.25	$269.30
Purchase #7	$95.48	13.772%	$108.6295	$108.63	$108.65	$108.60
7 purchase totals =	$786.43		$855.6748	$855.67	$855.70	$855.70