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	$113.72	5.354%	$119.8086	$119.81	$119.80	$119.80
Purchase #2	$123.98	6.746%	$132.3437	$132.34	$132.35	$132.30
Purchase #3	$246.33	3.286%	$254.4244	$254.42	$254.40	$254.40
Purchase #4	$105.53	3.383%	$109.1001	$109.10	$109.10	$109.10
Purchase #5	$101.45	4.291%	$105.8032	$105.80	$105.80	$105.80
Purchase #6	$21.92	11.502%	$24.4412	$24.44	$24.45	$24.40
Purchase #7	$247.58	3.720%	$256.79	$256.79	$256.80	$256.80
7 purchase totals =	$960.51		$1,002.7112	$1,002.70	$1,002.70	$1,002.60