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	$86.34	9.323%	$94.3895	$94.39	$94.40	$94.40
Purchase #2	$144.50	7.556%	$155.4184	$155.42	$155.40	$155.40
Purchase #3	$197.94	4.476%	$206.7998	$206.80	$206.80	$206.80
Purchase #4	$213.90	10.670%	$236.7231	$236.72	$236.70	$236.70
Purchase #5	$67.47	6.564%	$71.8987	$71.90	$71.90	$71.90
Purchase #6	$84.29	6.205%	$89.5202	$89.52	$89.50	$89.50
Purchase #7	$193.96	7.808%	$209.1044	$209.10	$209.10	$209.10
7 purchase totals =	$988.40		$1,063.8541	$1,063.85	$1,063.80	$1,063.80