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	$49.48	8.736%	$53.8026	$53.80	$53.80	$53.80
Purchase #2	$160.49	3.316%	$165.8118	$165.81	$165.80	$165.80
Purchase #3	$186.50	5.584%	$196.9142	$196.91	$196.90	$196.90
Purchase #4	$216.72	13.528%	$246.0379	$246.04	$246.05	$246.00
Purchase #5	$94.77	5.871%	$100.3339	$100.33	$100.35	$100.30
Purchase #6	$214.98	13.774%	$244.5913	$244.59	$244.60	$244.60
Purchase #7	$33.82	4.289%	$35.2705	$35.27	$35.25	$35.30
7 purchase totals =	$956.76		$1,042.7622	$1,042.75	$1,042.75	$1,042.70