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	$96.89	7.612%	$104.2653	$104.27	$104.25	$104.30
Purchase #2	$64.85	4.762%	$67.9382	$67.94	$67.95	$67.90
Purchase #3	$31.26	4.208%	$32.5754	$32.58	$32.60	$32.60
Purchase #4	$60.28	7.285%	$64.6714	$64.67	$64.65	$64.70
Purchase #5	$240.56	6.112%	$255.263	$255.26	$255.25	$255.30
Purchase #6	$157.67	10.262%	$173.8501	$173.85	$173.85	$173.90
Purchase #7	$82.91	6.462%	$88.2676	$88.27	$88.25	$88.30
7 purchase totals =	$734.42		$786.8310	$786.84	$786.80	$787.00