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	$127.76	3.207%	$131.8573	$131.86	$131.85	$131.90
Purchase #2	$99.98	6.405%	$106.3837	$106.38	$106.40	$106.40
Purchase #3	$228.77	4.409%	$238.8565	$238.86	$238.85	$238.90
Purchase #4	$136.96	4.656%	$143.3369	$143.34	$143.35	$143.30
Purchase #5	$248.54	11.460%	$277.0227	$277.02	$277.00	$277.00
Purchase #6	$153.59	4.355%	$160.2788	$160.28	$160.30	$160.30
Purchase #7	$68.98	10.407%	$76.1587	$76.16	$76.15	$76.20
7 purchase totals =	$1,064.58		$1,133.8946	$1,133.90	$1,133.90	$1,134.00