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	$222.45	5.714%	$235.1608	$235.16	$235.15	$235.20
Purchase #2	$91.33	3.511%	$94.5366	$94.54	$94.55	$94.50
Purchase #3	$16.96	6.772%	$18.1085	$18.11	$18.10	$18.10
Purchase #4	$146.43	6.708%	$156.2525	$156.25	$156.25	$156.30
Purchase #5	$158.49	6.455%	$168.7205	$168.72	$168.70	$168.70
Purchase #6	$148.73	4.481%	$155.3946	$155.39	$155.40	$155.40
Purchase #7	$213.65	9.281%	$233.4789	$233.48	$233.50	$233.50
7 purchase totals =	$998.04		$1,061.6524	$1,061.65	$1,061.65	$1,061.70