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	$206.34	4.358%	$215.3323	$215.33	$215.35	$215.30
Purchase #2	$12.31	6.620%	$13.1249	$13.12	$13.10	$13.10
Purchase #3	$149.37	13.549%	$169.6081	$169.61	$169.60	$169.60
Purchase #4	$77.72	5.747%	$82.1866	$82.19	$82.20	$82.20
Purchase #5	$37.79	4.819%	$39.6111	$39.61	$39.60	$39.60
Purchase #6	$198.82	12.492%	$223.6566	$223.66	$223.65	$223.70
Purchase #7	$138.38	6.538%	$147.4273	$147.43	$147.45	$147.40
7 purchase totals =	$820.73		$890.9469	$890.95	$890.95	$890.90