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	$72.34	11.738%	$80.8313	$80.83	$80.85	$80.80
Purchase #2	$204.50	3.660%	$211.9847	$211.98	$212.00	$212.00
Purchase #3	$186.63	13.336%	$211.519	$211.52	$211.50	$211.50
Purchase #4	$122.48	4.287%	$127.7307	$127.73	$127.75	$127.70
Purchase #5	$200.39	8.634%	$217.6917	$217.69	$217.70	$217.70
Purchase #6	$204.87	9.201%	$223.7201	$223.72	$223.70	$223.70
Purchase #7	$95.25	8.619%	$103.4596	$103.46	$103.45	$103.50
7 purchase totals =	$1,086.46		$1,176.9371	$1,176.93	$1,176.95	$1,176.90