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	$203.42	11.868%	$227.5619	$227.56	$227.55	$227.60
Purchase #2	$131.74	4.552%	$137.7368	$137.74	$137.75	$137.70
Purchase #3	$49.53	9.649%	$54.3091	$54.31	$54.30	$54.30
Purchase #4	$166.75	11.472%	$185.8796	$185.88	$185.90	$185.90
Purchase #5	$101.73	11.349%	$113.2753	$113.28	$113.30	$113.30
Purchase #6	$111.64	3.359%	$115.39	$115.39	$115.40	$115.40
Purchase #7	$187.47	11.109%	$208.296	$208.30	$208.30	$208.30
7 purchase totals =	$952.28		$1,042.4487	$1,042.46	$1,042.50	$1,042.50