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	$234.89	13.560%	$266.7411	$266.74	$266.75	$266.70
Purchase #2	$110.79	3.698%	$114.887	$114.89	$114.90	$114.90
Purchase #3	$59.85	8.121%	$64.7104	$64.71	$64.70	$64.70
Purchase #4	$61.36	6.256%	$65.1987	$65.20	$65.20	$65.20
Purchase #5	$180.64	8.664%	$196.2906	$196.29	$196.30	$196.30
Purchase #6	$117.42	9.293%	$128.3318	$128.33	$128.35	$128.30
Purchase #7	$203.28	7.415%	$218.3532	$218.35	$218.35	$218.40
7 purchase totals =	$968.23		$1,054.5128	$1,054.51	$1,054.55	$1,054.50