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	$230.95	13.495%	$262.1167	$262.12	$262.10	$262.10
Purchase #2	$109.31	11.221%	$121.5757	$121.58	$121.60	$121.60
Purchase #3	$30.71	11.543%	$34.2549	$34.25	$34.25	$34.30
Purchase #4	$127.36	3.372%	$131.6546	$131.65	$131.65	$131.70
Purchase #5	$25.93	4.593%	$27.121	$27.12	$27.10	$27.10
Purchase #6	$72.73	10.699%	$80.5114	$80.51	$80.50	$80.50
Purchase #7	$96.54	7.253%	$103.542	$103.54	$103.55	$103.50
7 purchase totals =	$693.53		$760.7763	$760.77	$760.75	$760.80