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	$188.84	6.162%	$200.4763	$200.48	$200.50	$200.50
Purchase #2	$180.32	6.487%	$192.0174	$192.02	$192.00	$192.00
Purchase #3	$218.71	7.222%	$234.5052	$234.51	$234.50	$234.50
Purchase #4	$155.40	7.132%	$166.4831	$166.48	$166.50	$166.50
Purchase #5	$150.48	11.837%	$168.2923	$168.29	$168.30	$168.30
Purchase #6	$27.69	8.176%	$29.9539	$29.95	$29.95	$30.00
Purchase #7	$171.54	6.315%	$182.3728	$182.37	$182.35	$182.40
7 purchase totals =	$1,092.98		$1,174.1010	$1,174.10	$1,174.10	$1,174.20