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	$41.37	7.843%	$44.6146	$44.61	$44.60	$44.60
Purchase #2	$42.45	6.723%	$45.3039	$45.30	$45.30	$45.30
Purchase #3	$70.26	3.226%	$72.5266	$72.53	$72.55	$72.50
Purchase #4	$72.27	5.173%	$76.0085	$76.01	$76.00	$76.00
Purchase #5	$47.74	7.623%	$51.3792	$51.38	$51.40	$51.40
Purchase #6	$165.61	3.589%	$171.5537	$171.55	$171.55	$171.60
Purchase #7	$78.58	8.290%	$85.0943	$85.09	$85.10	$85.10
7 purchase totals =	$518.28		$546.4808	$546.47	$546.50	$546.50