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	$174.76	4.575%	$182.7553	$182.76	$182.75	$182.80
Purchase #2	$56.30	5.623%	$59.4657	$59.47	$59.45	$59.50
Purchase #3	$91.52	9.394%	$100.1174	$100.12	$100.10	$100.10
Purchase #4	$172.55	6.356%	$183.5173	$183.52	$183.50	$183.50
Purchase #5	$115.91	5.626%	$122.4311	$122.43	$122.45	$122.40
Purchase #6	$132.53	4.717%	$138.7814	$138.78	$138.80	$138.80
Purchase #7	$206.27	7.811%	$222.3817	$222.38	$222.40	$222.40
7 purchase totals =	$949.84		$1,009.4499	$1,009.46	$1,009.45	$1,009.50