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	$184.80	12.337%	$207.5988	$207.60	$207.60	$207.60
Purchase #2	$228.64	10.173%	$251.8995	$251.90	$251.90	$251.90
Purchase #3	$110.69	11.759%	$123.706	$123.71	$123.70	$123.70
Purchase #4	$65.65	7.139%	$70.3368	$70.34	$70.35	$70.30
Purchase #5	$12.45	9.767%	$13.666	$13.67	$13.65	$13.70
Purchase #6	$126.65	3.820%	$131.488	$131.49	$131.50	$131.50
Purchase #7	$157.98	3.108%	$162.89	$162.89	$162.90	$162.90
7 purchase totals =	$886.86		$961.5851	$961.60	$961.60	$961.60