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	$99.75	3.791%	$103.5315	$103.53	$103.55	$103.50
Purchase #2	$18.93	5.120%	$19.8992	$19.90	$19.90	$19.90
Purchase #3	$165.80	5.697%	$175.2456	$175.25	$175.25	$175.20
Purchase #4	$136.91	7.750%	$147.5205	$147.52	$147.50	$147.50
Purchase #5	$52.61	12.793%	$59.3404	$59.34	$59.35	$59.30
Purchase #6	$50.82	4.306%	$53.0083	$53.01	$53.00	$53.00
Purchase #7	$129.67	13.466%	$147.1314	$147.13	$147.15	$147.10
7 purchase totals =	$654.49		$705.6769	$705.68	$705.70	$705.50