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	$179.37	5.375%	$189.0111	$189.01	$189.00	$189.00
Purchase #2	$167.86	13.626%	$190.7326	$190.73	$190.75	$190.70
Purchase #3	$54.99	11.578%	$61.3567	$61.36	$61.35	$61.40
Purchase #4	$76.51	4.271%	$79.7777	$79.78	$79.80	$79.80
Purchase #5	$107.43	12.427%	$120.7803	$120.78	$120.80	$120.80
Purchase #6	$173.45	13.317%	$196.5483	$196.55	$196.55	$196.50
Purchase #7	$163.87	3.497%	$169.6005	$169.60	$169.60	$169.60
7 purchase totals =	$923.48		$1,007.8072	$1,007.81	$1,007.85	$1,007.80