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	$102.83	7.247%	$110.2821	$110.28	$110.30	$110.30
Purchase #2	$142.83	5.276%	$150.3657	$150.37	$150.35	$150.40
Purchase #3	$188.36	8.258%	$203.9148	$203.91	$203.90	$203.90
Purchase #4	$233.54	12.140%	$261.8918	$261.89	$261.90	$261.90
Purchase #5	$88.83	4.577%	$92.8957	$92.90	$92.90	$92.90
Purchase #6	$81.43	11.217%	$90.564	$90.56	$90.55	$90.60
Purchase #7	$56.95	10.524%	$62.9434	$62.94	$62.95	$62.90
7 purchase totals =	$894.77		$972.8575	$972.85	$972.85	$972.90