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	$95.98	4.751%	$100.54	$100.54	$100.55	$100.50
Purchase #2	$168.95	6.430%	$179.8135	$179.81	$179.80	$179.80
Purchase #3	$249.77	13.223%	$282.7971	$282.80	$282.80	$282.80
Purchase #4	$87.64	13.126%	$99.1436	$99.14	$99.15	$99.10
Purchase #5	$52.33	12.739%	$58.9963	$59.00	$59.00	$59.00
Purchase #6	$237.81	5.746%	$251.4746	$251.47	$251.45	$251.50
Purchase #7	$92.83	10.171%	$102.2717	$102.27	$102.25	$102.30
7 purchase totals =	$985.31		$1,075.0368	$1,075.03	$1,075.00	$1,075.00