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	$230.58	10.369%	$254.4888	$254.49	$254.50	$254.50
Purchase #2	$166.46	4.858%	$174.5466	$174.55	$174.55	$174.50
Purchase #3	$33.89	13.455%	$38.4499	$38.45	$38.45	$38.40
Purchase #4	$35.68	4.264%	$37.2014	$37.20	$37.20	$37.20
Purchase #5	$126.27	12.465%	$142.0096	$142.01	$142.00	$142.00
Purchase #6	$247.52	13.571%	$281.1109	$281.11	$281.10	$281.10
Purchase #7	$77.90	13.501%	$88.4173	$88.42	$88.40	$88.40
7 purchase totals =	$918.30		$1,016.2245	$1,016.23	$1,016.20	$1,016.10