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	$165.29	3.820%	$171.6041	$171.60	$171.60	$171.60
Purchase #2	$52.68	12.218%	$59.1164	$59.12	$59.10	$59.10
Purchase #3	$40.95	6.646%	$43.6715	$43.67	$43.65	$43.70
Purchase #4	$172.33	10.321%	$190.1162	$190.12	$190.10	$190.10
Purchase #5	$180.42	8.479%	$195.7178	$195.72	$195.70	$195.70
Purchase #6	$60.39	10.122%	$66.5027	$66.50	$66.50	$66.50
Purchase #7	$28.66	10.409%	$31.6432	$31.64	$31.65	$31.60
7 purchase totals =	$700.72		$758.3719	$758.37	$758.30	$758.30