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	$71.87	8.544%	$78.0106	$78.01	$78.00	$78.00
Purchase #2	$100.33	10.675%	$111.0402	$111.04	$111.05	$111.00
Purchase #3	$249.51	6.127%	$264.7975	$264.80	$264.80	$264.80
Purchase #4	$151.65	12.159%	$170.0891	$170.09	$170.10	$170.10
Purchase #5	$200.65	7.421%	$215.5402	$215.54	$215.55	$215.50
Purchase #6	$131.64	12.175%	$147.6672	$147.67	$147.65	$147.70
Purchase #7	$59.27	8.495%	$64.305	$64.31	$64.30	$64.30
7 purchase totals =	$964.92		$1,051.4498	$1,051.46	$1,051.45	$1,051.40