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	$67.55	4.838%	$70.8181	$70.82	$70.80	$70.80
Purchase #2	$102.33	3.802%	$106.2206	$106.22	$106.20	$106.20
Purchase #3	$89.49	10.325%	$98.7298	$98.73	$98.75	$98.70
Purchase #4	$95.30	10.613%	$105.4142	$105.41	$105.40	$105.40
Purchase #5	$7.73	4.609%	$8.0863	$8.09	$8.10	$8.10
Purchase #6	$112.63	12.661%	$126.8901	$126.89	$126.90	$126.90
Purchase #7	$97.82	12.389%	$109.9389	$109.94	$109.95	$109.90
7 purchase totals =	$572.85		$626.0980	$626.10	$626.10	$626.00