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	$71.58	11.510%	$79.8189	$79.82	$79.80	$79.80
Purchase #2	$115.89	7.386%	$124.4496	$124.45	$124.45	$124.40
Purchase #3	$59.41	9.393%	$64.9904	$64.99	$65.00	$65.00
Purchase #4	$59.87	5.795%	$63.3395	$63.34	$63.35	$63.30
Purchase #5	$203.59	13.549%	$231.1744	$231.17	$231.15	$231.20
Purchase #6	$179.72	4.802%	$188.3502	$188.35	$188.35	$188.40
Purchase #7	$248.26	13.117%	$280.8243	$280.82	$280.80	$280.80
7 purchase totals =	$938.32		$1,032.9473	$1,032.94	$1,032.90	$1,032.90