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	$99.56	6.415%	$105.9468	$105.95	$105.95	$105.90
Purchase #2	$99.45	12.177%	$111.56	$111.56	$111.55	$111.60
Purchase #3	$102.46	6.272%	$108.8863	$108.89	$108.90	$108.90
Purchase #4	$217.78	13.758%	$247.7422	$247.74	$247.75	$247.70
Purchase #5	$144.74	9.718%	$158.8058	$158.81	$158.80	$158.80
Purchase #6	$23.58	8.494%	$25.5829	$25.58	$25.60	$25.60
Purchase #7	$130.53	8.623%	$141.7856	$141.79	$141.80	$141.80
7 purchase totals =	$818.10		$900.3096	$900.32	$900.35	$900.30