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	$48.53	7.585%	$52.211	$52.21	$52.20	$52.20
Purchase #2	$98.65	7.346%	$105.8968	$105.90	$105.90	$105.90
Purchase #3	$171.96	7.179%	$184.305	$184.31	$184.30	$184.30
Purchase #4	$72.50	7.646%	$78.0434	$78.04	$78.05	$78.00
Purchase #5	$196.68	9.599%	$215.5593	$215.56	$215.55	$215.60
Purchase #6	$220.87	12.862%	$249.2783	$249.28	$249.30	$249.30
Purchase #7	$50.54	9.206%	$55.1927	$55.19	$55.20	$55.20
7 purchase totals =	$859.73		$940.4865	$940.49	$940.50	$940.50