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	$159.96	9.208%	$174.6891	$174.69	$174.70	$174.70
Purchase #2	$203.45	8.819%	$221.3923	$221.39	$221.40	$221.40
Purchase #3	$138.42	5.294%	$145.748	$145.75	$145.75	$145.70
Purchase #4	$47.40	9.442%	$51.8755	$51.88	$51.90	$51.90
Purchase #5	$99.41	12.120%	$111.4585	$111.46	$111.45	$111.50
Purchase #6	$61.44	13.267%	$69.5912	$69.59	$69.60	$69.60
Purchase #7	$148.46	10.718%	$164.3719	$164.37	$164.35	$164.40
7 purchase totals =	$858.54		$939.1265	$939.13	$939.15	$939.20