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	$221.41	5.274%	$233.0872	$233.09	$233.10	$233.10
Purchase #2	$42.48	4.707%	$44.4795	$44.48	$44.50	$44.50
Purchase #3	$237.49	7.116%	$254.3898	$254.39	$254.40	$254.40
Purchase #4	$229.69	7.380%	$246.6411	$246.64	$246.65	$246.60
Purchase #5	$67.33	7.798%	$72.5804	$72.58	$72.60	$72.60
Purchase #6	$224.39	6.271%	$238.4615	$238.46	$238.45	$238.50
Purchase #7	$196.75	12.450%	$221.2454	$221.25	$221.25	$221.20
7 purchase totals =	$1,219.54		$1,310.8849	$1,310.89	$1,310.95	$1,310.90