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	$62.63	4.702%	$65.5749	$65.57	$65.55	$65.60
Purchase #2	$84.87	13.811%	$96.5914	$96.59	$96.60	$96.60
Purchase #3	$50.80	7.843%	$54.7842	$54.78	$54.80	$54.80
Purchase #4	$25.79	6.111%	$27.366	$27.37	$27.35	$27.40
Purchase #5	$153.87	10.419%	$169.9017	$169.90	$169.90	$169.90
Purchase #6	$141.89	11.804%	$158.6387	$158.64	$158.65	$158.60
Purchase #7	$208.72	9.373%	$228.2833	$228.28	$228.30	$228.30
7 purchase totals =	$728.57		$801.1402	$801.13	$801.15	$801.20