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	$156.43	11.355%	$174.1926	$174.19	$174.20	$174.20
Purchase #2	$41.76	4.107%	$43.4751	$43.48	$43.50	$43.50
Purchase #3	$6.62	4.106%	$6.8918	$6.89	$6.90	$6.90
Purchase #4	$201.51	11.549%	$224.7824	$224.78	$224.80	$224.80
Purchase #5	$48.39	9.326%	$52.9029	$52.90	$52.90	$52.90
Purchase #6	$66.96	7.270%	$71.828	$71.83	$71.85	$71.80
Purchase #7	$109.94	8.848%	$119.6675	$119.67	$119.65	$119.70
7 purchase totals =	$631.61		$693.7403	$693.74	$693.80	$693.80