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	$246.69	13.203%	$279.2605	$279.26	$279.25	$279.30
Purchase #2	$101.96	3.601%	$105.6316	$105.63	$105.65	$105.60
Purchase #3	$200.90	7.793%	$216.5561	$216.56	$216.55	$216.60
Purchase #4	$51.27	6.665%	$54.6871	$54.69	$54.70	$54.70
Purchase #5	$165.70	9.427%	$181.3205	$181.32	$181.30	$181.30
Purchase #6	$77.74	5.775%	$82.2295	$82.23	$82.25	$82.20
Purchase #7	$32.58	5.689%	$34.4335	$34.43	$34.45	$34.40
7 purchase totals =	$876.84		$954.1188	$954.12	$954.15	$954.10