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	$242.86	3.661%	$251.7511	$251.75	$251.75	$251.80
Purchase #2	$177.93	4.846%	$186.5525	$186.55	$186.55	$186.60
Purchase #3	$127.86	5.439%	$134.8143	$134.81	$134.80	$134.80
Purchase #4	$236.90	6.871%	$253.1774	$253.18	$253.20	$253.20
Purchase #5	$90.87	9.575%	$99.5708	$99.57	$99.55	$99.60
Purchase #6	$195.43	13.143%	$221.1154	$221.12	$221.10	$221.10
Purchase #7	$39.94	7.449%	$42.9151	$42.92	$42.90	$42.90
7 purchase totals =	$1,111.79		$1,189.8966	$1,189.90	$1,189.85	$1,190.00