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	$141.62	4.281%	$147.6828	$147.68	$147.70	$147.70
Purchase #2	$152.87	9.611%	$167.5623	$167.56	$167.55	$167.60
Purchase #3	$63.96	12.396%	$71.8885	$71.89	$71.90	$71.90
Purchase #4	$49.83	7.728%	$53.6809	$53.68	$53.70	$53.70
Purchase #5	$99.45	12.310%	$111.6923	$111.69	$111.70	$111.70
Purchase #6	$144.80	4.615%	$151.4825	$151.48	$151.50	$151.50
Purchase #7	$203.38	6.725%	$217.0573	$217.06	$217.05	$217.10
7 purchase totals =	$855.91		$921.0466	$921.04	$921.10	$921.20