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	$174.80	10.536%	$193.2169	$193.22	$193.20	$193.20
Purchase #2	$221.74	3.215%	$228.8689	$228.87	$228.85	$228.90
Purchase #3	$250.69	11.131%	$278.5943	$278.59	$278.60	$278.60
Purchase #4	$223.46	11.699%	$249.6026	$249.60	$249.60	$249.60
Purchase #5	$156.78	7.442%	$168.4476	$168.45	$168.45	$168.40
Purchase #6	$64.69	10.585%	$71.5374	$71.54	$71.55	$71.50
Purchase #7	$16.91	8.458%	$18.3402	$18.34	$18.35	$18.30
7 purchase totals =	$1,109.07		$1,208.6079	$1,208.61	$1,208.60	$1,208.50