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	$223.84	8.115%	$242.0046	$242.00	$242.00	$242.00
Purchase #2	$119.27	6.524%	$127.0512	$127.05	$127.05	$127.10
Purchase #3	$43.25	7.597%	$46.5357	$46.54	$46.55	$46.50
Purchase #4	$61.50	13.385%	$69.7318	$69.73	$69.75	$69.70
Purchase #5	$119.48	6.443%	$127.1781	$127.18	$127.20	$127.20
Purchase #6	$104.45	12.808%	$117.828	$117.83	$117.85	$117.80
Purchase #7	$236.93	7.771%	$255.3418	$255.34	$255.35	$255.30
7 purchase totals =	$908.72		$985.6712	$985.67	$985.75	$985.60