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	$71.53	9.469%	$78.3032	$78.30	$78.30	$78.30
Purchase #2	$63.44	6.764%	$67.7311	$67.73	$67.75	$67.70
Purchase #3	$89.96	10.525%	$99.4283	$99.43	$99.45	$99.40
Purchase #4	$189.67	10.116%	$208.857	$208.86	$208.85	$208.90
Purchase #5	$190.98	8.392%	$207.007	$207.01	$207.00	$207.00
Purchase #6	$58.79	11.344%	$65.4591	$65.46	$65.45	$65.50
Purchase #7	$219.51	3.222%	$226.5826	$226.58	$226.60	$226.60
7 purchase totals =	$883.88		$953.3683	$953.37	$953.40	$953.40