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	$147.38	8.473%	$159.8675	$159.87	$159.85	$159.90
Purchase #2	$50.77	5.262%	$53.4415	$53.44	$53.45	$53.40
Purchase #3	$215.56	10.127%	$237.3898	$237.39	$237.40	$237.40
Purchase #4	$57.64	12.870%	$65.0583	$65.06	$65.05	$65.10
Purchase #5	$162.74	13.626%	$184.915	$184.92	$184.90	$184.90
Purchase #6	$241.83	10.332%	$266.8159	$266.82	$266.80	$266.80
Purchase #7	$247.98	5.423%	$261.428	$261.43	$261.45	$261.40
7 purchase totals =	$1,123.90		$1,228.9160	$1,228.93	$1,228.90	$1,228.90