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	$44.39	5.466%	$46.8164	$46.82	$46.80	$46.80
Purchase #2	$114.76	8.398%	$124.3975	$124.40	$124.40	$124.40
Purchase #3	$71.26	11.404%	$79.3865	$79.39	$79.40	$79.40
Purchase #4	$24.53	4.218%	$25.5647	$25.56	$25.55	$25.60
Purchase #5	$113.43	8.802%	$123.4141	$123.41	$123.40	$123.40
Purchase #6	$92.27	9.116%	$100.6813	$100.68	$100.70	$100.70
Purchase #7	$123.90	6.279%	$131.6797	$131.68	$131.70	$131.70
7 purchase totals =	$584.54		$631.9402	$631.94	$631.95	$632.00