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	$155.93	6.838%	$166.5925	$166.59	$166.60	$166.60
Purchase #2	$57.45	8.363%	$62.2545	$62.25	$62.25	$62.30
Purchase #3	$107.40	3.600%	$111.2664	$111.27	$111.25	$111.30
Purchase #4	$148.36	13.348%	$168.1631	$168.16	$168.15	$168.20
Purchase #5	$226.46	4.698%	$237.0991	$237.10	$237.10	$237.10
Purchase #6	$177.93	4.140%	$185.2963	$185.30	$185.30	$185.30
Purchase #7	$31.27	3.369%	$32.3235	$32.32	$32.30	$32.30
7 purchase totals =	$904.80		$962.9954	$962.99	$962.95	$963.10