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	$147.44	11.529%	$164.4384	$164.44	$164.45	$164.40
Purchase #2	$243.77	12.749%	$274.8482	$274.85	$274.85	$274.80
Purchase #3	$87.96	8.807%	$95.7066	$95.71	$95.70	$95.70
Purchase #4	$130.55	8.735%	$141.9535	$141.95	$141.95	$142.00
Purchase #5	$167.40	13.604%	$190.1731	$190.17	$190.15	$190.20
Purchase #6	$174.72	12.664%	$196.8465	$196.85	$196.85	$196.80
Purchase #7	$76.25	4.727%	$79.8543	$79.85	$79.85	$79.90
7 purchase totals =	$1,028.09		$1,143.8206	$1,143.82	$1,143.80	$1,143.80