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	$212.58	13.122%	$240.4747	$240.47	$240.45	$240.50
Purchase #2	$250.62	4.506%	$261.9129	$261.91	$261.90	$261.90
Purchase #3	$175.50	12.136%	$196.7987	$196.80	$196.80	$196.80
Purchase #4	$149.54	3.456%	$154.7081	$154.71	$154.70	$154.70
Purchase #5	$104.45	4.759%	$109.4208	$109.42	$109.40	$109.40
Purchase #6	$70.88	10.690%	$78.4571	$78.46	$78.45	$78.50
Purchase #7	$25.38	6.512%	$27.0327	$27.03	$27.05	$27.00
7 purchase totals =	$988.95		$1,068.8050	$1,068.80	$1,068.75	$1,068.80