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	$75.47	9.458%	$82.608	$82.61	$82.60	$82.60
Purchase #2	$52.28	8.540%	$56.7447	$56.74	$56.75	$56.70
Purchase #3	$68.83	9.237%	$75.1878	$75.19	$75.20	$75.20
Purchase #4	$38.82	9.550%	$42.5273	$42.53	$42.55	$42.50
Purchase #5	$95.61	9.697%	$104.8813	$104.88	$104.90	$104.90
Purchase #6	$123.38	4.321%	$128.7112	$128.71	$128.70	$128.70
Purchase #7	$61.43	5.781%	$64.9813	$64.98	$65.00	$65.00
7 purchase totals =	$515.82		$555.6416	$555.64	$555.70	$555.60