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	$18.48	6.417%	$19.6659	$19.67	$19.65	$19.70
Purchase #2	$10.54	12.113%	$11.8167	$11.82	$11.80	$11.80
Purchase #3	$195.38	12.356%	$219.5212	$219.52	$219.50	$219.50
Purchase #4	$180.40	5.522%	$190.3617	$190.36	$190.35	$190.40
Purchase #5	$158.91	4.768%	$166.4868	$166.49	$166.50	$166.50
Purchase #6	$92.89	4.288%	$96.8731	$96.87	$96.85	$96.90
Purchase #7	$179.64	4.280%	$187.3286	$187.33	$187.35	$187.30
7 purchase totals =	$836.24		$892.0540	$892.06	$892.00	$892.10