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	$141.86	5.721%	$149.9758	$149.98	$150.00	$150.00
Purchase #2	$215.84	5.656%	$228.0479	$228.05	$228.05	$228.00
Purchase #3	$82.34	10.266%	$90.793	$90.79	$90.80	$90.80
Purchase #4	$246.59	6.475%	$262.5567	$262.56	$262.55	$262.60
Purchase #5	$27.99	4.301%	$29.1938	$29.19	$29.20	$29.20
Purchase #6	$151.32	13.677%	$172.016	$172.02	$172.00	$172.00
Purchase #7	$167.76	13.684%	$190.7163	$190.72	$190.70	$190.70
7 purchase totals =	$1,033.70		$1,123.2995	$1,123.31	$1,123.30	$1,123.30