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	$235.88	13.260%	$267.1577	$267.16	$267.15	$267.20
Purchase #2	$69.61	13.365%	$78.9134	$78.91	$78.90	$78.90
Purchase #3	$22.75	11.511%	$25.3688	$25.37	$25.35	$25.40
Purchase #4	$215.88	10.617%	$238.8	$238.80	$238.80	$238.80
Purchase #5	$67.86	4.869%	$71.1641	$71.16	$71.15	$71.20
Purchase #6	$228.85	13.439%	$259.6052	$259.61	$259.60	$259.60
Purchase #7	$167.52	10.201%	$184.6087	$184.61	$184.60	$184.60
7 purchase totals =	$1,008.35		$1,125.6179	$1,125.62	$1,125.55	$1,125.70