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	$5.44	6.111%	$5.7724	$5.77	$5.75	$5.80
Purchase #2	$63.88	6.323%	$67.9191	$67.92	$67.90	$67.90
Purchase #3	$152.37	13.207%	$172.4935	$172.49	$172.50	$172.50
Purchase #4	$127.90	10.544%	$141.3858	$141.39	$141.40	$141.40
Purchase #5	$184.99	8.423%	$200.5717	$200.57	$200.55	$200.60
Purchase #6	$96.86	4.156%	$100.8855	$100.89	$100.90	$100.90
Purchase #7	$11.33	5.747%	$11.9811	$11.98	$12.00	$12.00
7 purchase totals =	$642.77		$701.0091	$701.01	$701.00	$701.10