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	$56.74	10.749%	$62.839	$62.84	$62.85	$62.80
Purchase #2	$223.42	10.828%	$247.6119	$247.61	$247.60	$247.60
Purchase #3	$112.27	6.529%	$119.6001	$119.60	$119.60	$119.60
Purchase #4	$173.76	5.227%	$182.8424	$182.84	$182.85	$182.80
Purchase #5	$70.31	10.724%	$77.85	$77.85	$77.85	$77.90
Purchase #6	$38.84	8.816%	$42.2641	$42.26	$42.25	$42.30
Purchase #7	$41.34	4.749%	$43.3032	$43.30	$43.30	$43.30
7 purchase totals =	$716.68		$776.3107	$776.30	$776.30	$776.30