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	$119.62	6.786%	$127.7374	$127.74	$127.75	$127.70
Purchase #2	$185.61	7.775%	$200.0412	$200.04	$200.05	$200.00
Purchase #3	$43.31	3.676%	$44.9021	$44.90	$44.90	$44.90
Purchase #4	$46.27	11.403%	$51.5462	$51.55	$51.55	$51.50
Purchase #5	$204.87	7.230%	$219.6821	$219.68	$219.70	$219.70
Purchase #6	$80.62	11.229%	$89.6728	$89.67	$89.65	$89.70
Purchase #7	$83.93	8.608%	$91.1547	$91.15	$91.15	$91.20
7 purchase totals =	$764.23		$824.7365	$824.73	$824.75	$824.70