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	$90.63	7.854%	$97.7481	$97.75	$97.75	$97.70
Purchase #2	$225.92	12.595%	$254.3746	$254.37	$254.35	$254.40
Purchase #3	$224.72	9.449%	$245.9538	$245.95	$245.95	$246.00
Purchase #4	$154.91	6.390%	$164.8087	$164.81	$164.80	$164.80
Purchase #5	$91.93	6.842%	$98.2199	$98.22	$98.20	$98.20
Purchase #6	$41.26	3.162%	$42.5646	$42.56	$42.55	$42.60
Purchase #7	$126.60	11.783%	$141.5173	$141.52	$141.50	$141.50
7 purchase totals =	$955.97		$1,045.1870	$1,045.18	$1,045.10	$1,045.20