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	$22.34	5.775%	$23.6301	$23.63	$23.65	$23.60
Purchase #2	$145.25	11.755%	$162.3241	$162.32	$162.30	$162.30
Purchase #3	$89.43	7.866%	$96.4646	$96.46	$96.45	$96.50
Purchase #4	$176.34	4.366%	$184.039	$184.04	$184.05	$184.00
Purchase #5	$174.90	7.806%	$188.5527	$188.55	$188.55	$188.60
Purchase #6	$64.96	11.385%	$72.3557	$72.36	$72.35	$72.40
Purchase #7	$100.79	10.336%	$111.2077	$111.21	$111.20	$111.20
7 purchase totals =	$774.01		$838.5739	$838.57	$838.55	$838.60