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	$17.52	8.156%	$18.9489	$18.95	$18.95	$18.90
Purchase #2	$179.71	9.387%	$196.5794	$196.58	$196.60	$196.60
Purchase #3	$227.90	10.456%	$251.7292	$251.73	$251.75	$251.70
Purchase #4	$70.89	10.576%	$78.3873	$78.39	$78.40	$78.40
Purchase #5	$242.33	10.488%	$267.7456	$267.75	$267.75	$267.70
Purchase #6	$104.82	4.262%	$109.2874	$109.29	$109.30	$109.30
Purchase #7	$198.39	12.483%	$223.155	$223.16	$223.15	$223.20
7 purchase totals =	$1,041.56		$1,145.8328	$1,145.85	$1,145.90	$1,145.80