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	$94.97	4.568%	$99.3082	$99.31	$99.30	$99.30
Purchase #2	$167.35	11.112%	$185.9459	$185.95	$185.95	$185.90
Purchase #3	$71.78	11.398%	$79.9615	$79.96	$79.95	$80.00
Purchase #4	$100.59	5.238%	$105.8589	$105.86	$105.85	$105.90
Purchase #5	$43.74	5.420%	$46.1107	$46.11	$46.10	$46.10
Purchase #6	$145.94	8.549%	$158.4164	$158.42	$158.40	$158.40
Purchase #7	$23.78	8.728%	$25.8555	$25.86	$25.85	$25.90
7 purchase totals =	$648.15		$701.4571	$701.47	$701.40	$701.50