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	$98.46	8.254%	$106.5869	$106.59	$106.60	$106.60
Purchase #2	$85.59	4.576%	$89.5066	$89.51	$89.50	$89.50
Purchase #3	$167.42	10.314%	$184.6877	$184.69	$184.70	$184.70
Purchase #4	$70.56	5.309%	$74.306	$74.31	$74.30	$74.30
Purchase #5	$139.33	3.691%	$144.4727	$144.47	$144.45	$144.50
Purchase #6	$176.57	12.327%	$198.3358	$198.34	$198.35	$198.30
Purchase #7	$186.78	5.364%	$196.7989	$196.80	$196.80	$196.80
7 purchase totals =	$924.71		$994.6946	$994.71	$994.70	$994.70