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	$150.68	7.812%	$162.4511	$162.45	$162.45	$162.50
Purchase #2	$82.88	4.486%	$86.598	$86.60	$86.60	$86.60
Purchase #3	$131.34	3.803%	$136.3349	$136.33	$136.35	$136.30
Purchase #4	$136.98	10.554%	$151.4369	$151.44	$151.45	$151.40
Purchase #5	$73.39	3.823%	$76.1957	$76.20	$76.20	$76.20
Purchase #6	$110.72	11.535%	$123.4916	$123.49	$123.50	$123.50
Purchase #7	$64.80	7.649%	$69.7566	$69.76	$69.75	$69.80
7 purchase totals =	$750.79		$806.2648	$806.27	$806.30	$806.30