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	$202.79	7.690%	$218.3846	$218.38	$218.40	$218.40
Purchase #2	$143.90	7.614%	$154.8565	$154.86	$154.85	$154.90
Purchase #3	$74.99	7.199%	$80.3885	$80.39	$80.40	$80.40
Purchase #4	$104.78	4.728%	$109.734	$109.73	$109.75	$109.70
Purchase #5	$235.54	13.206%	$266.6454	$266.65	$266.65	$266.60
Purchase #6	$102.99	8.162%	$111.396	$111.40	$111.40	$111.40
Purchase #7	$158.90	4.187%	$165.5531	$165.55	$165.55	$165.60
7 purchase totals =	$1,023.89		$1,106.9581	$1,106.96	$1,107.00	$1,107.00