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	$104.61	6.527%	$111.4379	$111.44	$111.45	$111.40
Purchase #2	$52.27	4.477%	$54.6101	$54.61	$54.60	$54.60
Purchase #3	$29.41	5.413%	$31.002	$31.00	$31.00	$31.00
Purchase #4	$165.57	8.426%	$179.5209	$179.52	$179.50	$179.50
Purchase #5	$181.64	5.534%	$191.692	$191.69	$191.70	$191.70
Purchase #6	$239.27	11.843%	$267.6067	$267.61	$267.60	$267.60
Purchase #7	$175.27	11.105%	$194.7337	$194.73	$194.75	$194.70
7 purchase totals =	$948.04		$1,030.6033	$1,030.60	$1,030.60	$1,030.50