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	$201.93	9.676%	$221.4687	$221.47	$221.45	$221.50
Purchase #2	$86.61	5.256%	$91.1622	$91.16	$91.15	$91.20
Purchase #3	$142.63	9.199%	$155.7505	$155.75	$155.75	$155.80
Purchase #4	$123.67	3.123%	$127.5322	$127.53	$127.55	$127.50
Purchase #5	$219.60	11.692%	$245.2756	$245.28	$245.30	$245.30
Purchase #6	$176.33	4.835%	$184.8556	$184.86	$184.85	$184.90
Purchase #7	$55.35	8.223%	$59.9014	$59.90	$59.90	$59.90
7 purchase totals =	$1,006.12		$1,085.9462	$1,085.95	$1,085.95	$1,086.10