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	$123.69	10.367%	$136.5129	$136.51	$136.50	$136.50
Purchase #2	$17.47	12.147%	$19.5921	$19.59	$19.60	$19.60
Purchase #3	$239.38	4.622%	$250.4441	$250.44	$250.45	$250.40
Purchase #4	$49.59	10.578%	$54.8356	$54.84	$54.85	$54.80
Purchase #5	$155.45	4.567%	$162.5494	$162.55	$162.55	$162.50
Purchase #6	$203.83	9.667%	$223.5342	$223.53	$223.55	$223.50
Purchase #7	$250.49	4.143%	$260.8678	$260.87	$260.85	$260.90
7 purchase totals =	$1,039.90		$1,108.3361	$1,108.33	$1,108.35	$1,108.20