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	$104.78	11.292%	$116.6118	$116.61	$116.60	$116.60
Purchase #2	$240.43	7.824%	$259.2412	$259.24	$259.25	$259.20
Purchase #3	$75.76	6.152%	$80.4208	$80.42	$80.40	$80.40
Purchase #4	$150.94	13.750%	$171.6943	$171.69	$171.70	$171.70
Purchase #5	$72.32	8.761%	$78.656	$78.66	$78.65	$78.70
Purchase #6	$120.61	6.512%	$128.4641	$128.46	$128.45	$128.50
Purchase #7	$165.66	7.546%	$178.1607	$178.16	$178.15	$178.20
7 purchase totals =	$930.50		$1,013.2489	$1,013.24	$1,013.20	$1,013.30