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	$96.92	9.121%	$105.7601	$105.76	$105.75	$105.80
Purchase #2	$64.89	4.517%	$67.8211	$67.82	$67.80	$67.80
Purchase #3	$95.25	11.664%	$106.36	$106.36	$106.35	$106.40
Purchase #4	$233.37	12.746%	$263.1153	$263.12	$263.10	$263.10
Purchase #5	$140.42	3.649%	$145.5439	$145.54	$145.55	$145.50
Purchase #6	$200.93	10.693%	$222.4154	$222.42	$222.40	$222.40
Purchase #7	$73.90	3.727%	$76.6543	$76.65	$76.65	$76.70
7 purchase totals =	$905.68		$987.6701	$987.67	$987.60	$987.70