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	$219.50	10.812%	$243.2323	$243.23	$243.25	$243.20
Purchase #2	$109.90	5.220%	$115.6368	$115.64	$115.65	$115.60
Purchase #3	$235.69	8.407%	$255.5045	$255.50	$255.50	$255.50
Purchase #4	$34.70	8.343%	$37.595	$37.60	$37.60	$37.60
Purchase #5	$158.82	12.664%	$178.933	$178.93	$178.95	$178.90
Purchase #6	$99.51	9.375%	$108.8391	$108.84	$108.85	$108.80
Purchase #7	$116.78	6.460%	$124.324	$124.32	$124.30	$124.30
7 purchase totals =	$974.90		$1,064.0647	$1,064.06	$1,064.10	$1,063.90