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	$181.55	8.436%	$196.8656	$196.87	$196.85	$196.90
Purchase #2	$50.46	10.522%	$55.7694	$55.77	$55.75	$55.80
Purchase #3	$168.28	5.335%	$177.2577	$177.26	$177.25	$177.30
Purchase #4	$205.65	10.649%	$227.5497	$227.55	$227.55	$227.50
Purchase #5	$88.50	12.510%	$99.5714	$99.57	$99.55	$99.60
Purchase #6	$6.60	8.710%	$7.1749	$7.17	$7.15	$7.20
Purchase #7	$175.50	8.450%	$190.3298	$190.33	$190.35	$190.30
7 purchase totals =	$876.54		$954.5185	$954.52	$954.45	$954.60