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	$104.70	13.749%	$119.0952	$119.10	$119.10	$119.10
Purchase #2	$51.65	8.857%	$56.2246	$56.22	$56.20	$56.20
Purchase #3	$62.61	11.561%	$69.8483	$69.85	$69.85	$69.80
Purchase #4	$162.78	5.216%	$171.2706	$171.27	$171.25	$171.30
Purchase #5	$209.56	5.717%	$221.5405	$221.54	$221.55	$221.50
Purchase #6	$196.57	11.310%	$218.8021	$218.80	$218.80	$218.80
Purchase #7	$205.29	11.247%	$228.379	$228.38	$228.40	$228.40
7 purchase totals =	$993.16		$1,085.1603	$1,085.16	$1,085.15	$1,085.10