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	$52.48	6.597%	$55.9421	$55.94	$55.95	$55.90
Purchase #2	$17.89	7.817%	$19.2885	$19.29	$19.30	$19.30
Purchase #3	$122.88	7.730%	$132.3786	$132.38	$132.40	$132.40
Purchase #4	$49.27	6.310%	$52.3789	$52.38	$52.40	$52.40
Purchase #5	$53.84	10.272%	$59.3704	$59.37	$59.35	$59.40
Purchase #6	$45.56	4.481%	$47.6015	$47.60	$47.60	$47.60
Purchase #7	$72.95	7.403%	$78.3505	$78.35	$78.35	$78.40
7 purchase totals =	$414.87		$445.3105	$445.31	$445.35	$445.40