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	$179.40	9.698%	$196.7982	$196.80	$196.80	$196.80
Purchase #2	$232.97	12.600%	$262.3242	$262.32	$262.30	$262.30
Purchase #3	$189.60	4.549%	$198.2249	$198.22	$198.20	$198.20
Purchase #4	$25.45	6.526%	$27.1109	$27.11	$27.10	$27.10
Purchase #5	$133.85	9.132%	$146.0732	$146.07	$146.05	$146.10
Purchase #6	$74.29	8.168%	$80.358	$80.36	$80.35	$80.40
Purchase #7	$186.95	5.240%	$196.7462	$196.75	$196.75	$196.70
7 purchase totals =	$1,022.51		$1,107.6356	$1,107.63	$1,107.55	$1,107.60