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	$117.43	11.661%	$131.1235	$131.12	$131.10	$131.10
Purchase #2	$29.74	7.320%	$31.917	$31.92	$31.90	$31.90
Purchase #3	$83.81	3.267%	$86.5481	$86.55	$86.55	$86.50
Purchase #4	$17.81	12.372%	$20.0135	$20.01	$20.00	$20.00
Purchase #5	$206.34	10.525%	$228.0573	$228.06	$228.05	$228.10
Purchase #6	$241.55	10.757%	$267.5335	$267.53	$267.55	$267.50
Purchase #7	$127.66	11.847%	$142.7839	$142.78	$142.80	$142.80
7 purchase totals =	$824.34		$907.9768	$907.97	$907.95	$907.90