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	$109.98	8.535%	$119.3668	$119.37	$119.35	$119.40
Purchase #2	$158.40	4.191%	$165.0385	$165.04	$165.05	$165.00
Purchase #3	$19.91	4.855%	$20.8766	$20.88	$20.90	$20.90
Purchase #4	$107.79	7.257%	$115.6123	$115.61	$115.60	$115.60
Purchase #5	$87.77	4.822%	$92.0023	$92.00	$92.00	$92.00
Purchase #6	$98.47	7.408%	$105.7647	$105.76	$105.75	$105.80
Purchase #7	$222.72	6.236%	$236.6088	$236.61	$236.60	$236.60
7 purchase totals =	$805.04		$855.2700	$855.27	$855.25	$855.30