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	$54.93	3.173%	$56.6729	$56.67	$56.65	$56.70
Purchase #2	$227.43	3.219%	$234.751	$234.75	$234.75	$234.80
Purchase #3	$73.93	4.769%	$77.4557	$77.46	$77.45	$77.50
Purchase #4	$69.33	13.655%	$78.797	$78.80	$78.80	$78.80
Purchase #5	$69.92	3.164%	$72.1323	$72.13	$72.15	$72.10
Purchase #6	$157.37	10.267%	$173.5272	$173.53	$173.55	$173.50
Purchase #7	$215.57	11.314%	$239.9596	$239.96	$239.95	$240.00
7 purchase totals =	$868.48		$933.2957	$933.30	$933.30	$933.40