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	$55.92	6.601%	$59.6113	$59.61	$59.60	$59.60
Purchase #2	$111.99	6.515%	$119.2861	$119.29	$119.30	$119.30
Purchase #3	$205.72	3.423%	$212.7618	$212.76	$212.75	$212.80
Purchase #4	$94.78	12.774%	$106.8872	$106.89	$106.90	$106.90
Purchase #5	$166.25	6.654%	$177.3123	$177.31	$177.30	$177.30
Purchase #6	$80.93	13.745%	$92.0538	$92.05	$92.05	$92.10
Purchase #7	$42.52	6.730%	$45.3816	$45.38	$45.40	$45.40
7 purchase totals =	$758.11		$813.2941	$813.29	$813.30	$813.40