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	$108.36	5.592%	$114.4195	$114.42	$114.40	$114.40
Purchase #2	$56.88	8.540%	$61.7376	$61.74	$61.75	$61.70
Purchase #3	$184.76	3.627%	$191.4612	$191.46	$191.45	$191.50
Purchase #4	$174.31	7.590%	$187.5401	$187.54	$187.55	$187.50
Purchase #5	$87.80	8.801%	$95.5273	$95.53	$95.55	$95.50
Purchase #6	$54.59	9.290%	$59.6614	$59.66	$59.65	$59.70
Purchase #7	$28.61	11.147%	$31.7992	$31.80	$31.80	$31.80
7 purchase totals =	$695.31		$742.1463	$742.15	$742.15	$742.10