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	$204.61	13.266%	$231.7536	$231.75	$231.75	$231.80
Purchase #2	$77.77	10.540%	$85.967	$85.97	$85.95	$86.00
Purchase #3	$51.53	9.233%	$56.2878	$56.29	$56.30	$56.30
Purchase #4	$129.44	9.366%	$141.5634	$141.56	$141.55	$141.60
Purchase #5	$77.32	12.360%	$86.8768	$86.88	$86.90	$86.90
Purchase #6	$130.31	8.218%	$141.0189	$141.02	$141.00	$141.00
Purchase #7	$27.59	3.482%	$28.5507	$28.55	$28.55	$28.60
7 purchase totals =	$698.57		$772.0182	$772.02	$772.00	$772.20