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	$140.91	7.732%	$151.8052	$151.81	$151.80	$151.80
Purchase #2	$171.44	11.845%	$191.7471	$191.75	$191.75	$191.70
Purchase #3	$224.64	11.392%	$250.231	$250.23	$250.25	$250.20
Purchase #4	$13.74	13.864%	$15.6449	$15.64	$15.65	$15.60
Purchase #5	$55.63	6.854%	$59.4429	$59.44	$59.45	$59.40
Purchase #6	$123.41	7.308%	$132.4288	$132.43	$132.45	$132.40
Purchase #7	$163.70	4.624%	$171.2695	$171.27	$171.25	$171.30
7 purchase totals =	$893.47		$972.5694	$972.57	$972.60	$972.40