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	$168.71	6.292%	$179.3252	$179.33	$179.35	$179.30
Purchase #2	$223.78	4.330%	$233.4697	$233.47	$233.45	$233.50
Purchase #3	$177.95	11.576%	$198.5495	$198.55	$198.55	$198.50
Purchase #4	$87.40	12.474%	$98.3023	$98.30	$98.30	$98.30
Purchase #5	$91.40	13.744%	$103.962	$103.96	$103.95	$104.00
Purchase #6	$59.83	7.843%	$64.5225	$64.52	$64.50	$64.50
Purchase #7	$35.75	10.415%	$39.4734	$39.47	$39.45	$39.50
7 purchase totals =	$844.82		$917.6046	$917.60	$917.55	$917.60