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	$179.95	11.629%	$200.8764	$200.88	$200.90	$200.90
Purchase #2	$150.36	11.717%	$167.9777	$167.98	$168.00	$168.00
Purchase #3	$80.72	11.772%	$90.2224	$90.22	$90.20	$90.20
Purchase #4	$200.25	7.655%	$215.5791	$215.58	$215.60	$215.60
Purchase #5	$169.38	9.244%	$185.0375	$185.04	$185.05	$185.00
Purchase #6	$117.74	9.484%	$128.9065	$128.91	$128.90	$128.90
Purchase #7	$52.40	12.450%	$58.9238	$58.92	$58.90	$58.90
7 purchase totals =	$950.80		$1,047.5234	$1,047.53	$1,047.55	$1,047.50