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	$156.52	5.118%	$164.5307	$164.53	$164.55	$164.50
Purchase #2	$205.63	5.309%	$216.5469	$216.55	$216.55	$216.50
Purchase #3	$156.81	5.110%	$164.823	$164.82	$164.80	$164.80
Purchase #4	$221.96	8.540%	$240.9154	$240.92	$240.90	$240.90
Purchase #5	$148.81	5.430%	$156.8904	$156.89	$156.90	$156.90
Purchase #6	$47.64	4.420%	$49.7457	$49.75	$49.75	$49.70
Purchase #7	$218.57	13.532%	$248.1469	$248.15	$248.15	$248.10
7 purchase totals =	$1,155.94		$1,241.5990	$1,241.61	$1,241.60	$1,241.40