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	$102.47	9.838%	$112.551	$112.55	$112.55	$112.60
Purchase #2	$6.66	4.710%	$6.9737	$6.97	$6.95	$7.00
Purchase #3	$165.83	5.557%	$175.0452	$175.05	$175.05	$175.00
Purchase #4	$31.49	7.223%	$33.7645	$33.76	$33.75	$33.80
Purchase #5	$105.58	6.321%	$112.2537	$112.25	$112.25	$112.30
Purchase #6	$113.38	5.680%	$119.82	$119.82	$119.80	$119.80
Purchase #7	$36.46	5.595%	$38.4999	$38.50	$38.50	$38.50
7 purchase totals =	$561.87		$598.9080	$598.90	$598.85	$599.00