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	$59.65	9.355%	$65.2303	$65.23	$65.25	$65.20
Purchase #2	$103.53	3.322%	$106.9693	$106.97	$106.95	$107.00
Purchase #3	$138.62	4.200%	$144.442	$144.44	$144.45	$144.40
Purchase #4	$128.83	9.664%	$141.2801	$141.28	$141.30	$141.30
Purchase #5	$157.46	6.354%	$167.465	$167.47	$167.45	$167.50
Purchase #6	$155.58	9.511%	$170.3772	$170.38	$170.40	$170.40
Purchase #7	$246.37	3.689%	$255.4586	$255.46	$255.45	$255.50
7 purchase totals =	$990.04		$1,051.2225	$1,051.23	$1,051.25	$1,051.30