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	$133.64	3.385%	$138.1637	$138.16	$138.15	$138.20
Purchase #2	$158.85	6.329%	$168.9036	$168.90	$168.90	$168.90
Purchase #3	$62.97	13.442%	$71.4344	$71.43	$71.45	$71.40
Purchase #4	$183.66	8.654%	$199.5539	$199.55	$199.55	$199.60
Purchase #5	$234.77	11.764%	$262.3883	$262.39	$262.40	$262.40
Purchase #6	$50.47	11.360%	$56.2034	$56.20	$56.20	$56.20
Purchase #7	$114.64	13.638%	$130.2746	$130.27	$130.25	$130.30
7 purchase totals =	$939.00		$1,026.9219	$1,026.90	$1,026.90	$1,027.00