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	$167.52	12.605%	$188.6359	$188.64	$188.65	$188.60
Purchase #2	$181.71	4.779%	$190.3939	$190.39	$190.40	$190.40
Purchase #3	$169.37	8.272%	$183.3803	$183.38	$183.40	$183.40
Purchase #4	$215.92	3.487%	$223.4491	$223.45	$223.45	$223.40
Purchase #5	$152.29	8.304%	$164.9362	$164.94	$164.95	$164.90
Purchase #6	$38.35	5.392%	$40.4178	$40.42	$40.40	$40.40
Purchase #7	$62.30	9.594%	$68.2771	$68.28	$68.30	$68.30
7 purchase totals =	$987.46		$1,059.4903	$1,059.50	$1,059.55	$1,059.40