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	$20.64	5.830%	$21.8433	$21.84	$21.85	$21.80
Purchase #2	$33.61	6.813%	$35.8998	$35.90	$35.90	$35.90
Purchase #3	$177.27	4.120%	$184.5735	$184.57	$184.55	$184.60
Purchase #4	$236.25	13.300%	$267.6713	$267.67	$267.65	$267.70
Purchase #5	$115.47	10.480%	$127.5713	$127.57	$127.55	$127.60
Purchase #6	$166.91	8.659%	$181.3627	$181.36	$181.35	$181.40
Purchase #7	$167.79	8.726%	$182.4314	$182.43	$182.45	$182.40
7 purchase totals =	$917.94		$1,001.3533	$1,001.34	$1,001.30	$1,001.40