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	$67.84	12.627%	$76.4062	$76.41	$76.40	$76.40
Purchase #2	$198.26	6.767%	$211.6763	$211.68	$211.70	$211.70
Purchase #3	$75.52	4.464%	$78.8912	$78.89	$78.90	$78.90
Purchase #4	$41.96	10.404%	$46.3255	$46.33	$46.35	$46.30
Purchase #5	$221.84	5.390%	$233.7972	$233.80	$233.80	$233.80
Purchase #6	$129.74	7.591%	$139.5886	$139.59	$139.60	$139.60
Purchase #7	$232.80	9.870%	$255.7774	$255.78	$255.80	$255.80
7 purchase totals =	$967.96		$1,042.4624	$1,042.48	$1,042.55	$1,042.50