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	$59.54	13.565%	$67.6166	$67.62	$67.60	$67.60
Purchase #2	$54.66	6.123%	$58.0068	$58.01	$58.00	$58.00
Purchase #3	$208.25	9.719%	$228.4898	$228.49	$228.50	$228.50
Purchase #4	$37.74	13.692%	$42.9074	$42.91	$42.90	$42.90
Purchase #5	$204.88	4.292%	$213.6734	$213.67	$213.65	$213.70
Purchase #6	$100.44	13.162%	$113.6599	$113.66	$113.65	$113.70
Purchase #7	$158.94	4.384%	$165.9079	$165.91	$165.90	$165.90
7 purchase totals =	$824.45		$890.2618	$890.27	$890.20	$890.30