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	$84.61	5.581%	$89.3321	$89.33	$89.35	$89.30
Purchase #2	$11.78	5.247%	$12.3981	$12.40	$12.40	$12.40
Purchase #3	$216.84	12.722%	$244.4264	$244.43	$244.45	$244.40
Purchase #4	$69.25	5.183%	$72.8392	$72.84	$72.85	$72.80
Purchase #5	$186.70	6.498%	$198.8318	$198.83	$198.85	$198.80
Purchase #6	$6.30	4.702%	$6.5962	$6.60	$6.60	$6.60
Purchase #7	$69.67	4.136%	$72.5516	$72.55	$72.55	$72.60
7 purchase totals =	$645.15		$696.9754	$696.98	$697.05	$696.90