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	$148.27	5.426%	$156.3151	$156.32	$156.30	$156.30
Purchase #2	$235.71	7.350%	$253.0347	$253.03	$253.05	$253.00
Purchase #3	$186.94	12.141%	$209.6364	$209.64	$209.65	$209.60
Purchase #4	$92.93	12.422%	$104.4738	$104.47	$104.45	$104.50
Purchase #5	$56.28	9.555%	$61.6576	$61.66	$61.65	$61.70
Purchase #6	$145.78	6.277%	$154.9306	$154.93	$154.95	$154.90
Purchase #7	$113.92	5.231%	$119.8792	$119.88	$119.90	$119.90
7 purchase totals =	$979.83		$1,059.9274	$1,059.93	$1,059.95	$1,059.90