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	$45.34	5.400%	$47.7884	$47.79	$47.80	$47.80
Purchase #2	$144.87	4.557%	$151.4717	$151.47	$151.45	$151.50
Purchase #3	$135.54	11.565%	$151.2152	$151.22	$151.20	$151.20
Purchase #4	$131.51	8.636%	$142.8672	$142.87	$142.85	$142.90
Purchase #5	$193.56	10.113%	$213.1347	$213.13	$213.15	$213.10
Purchase #6	$240.27	9.469%	$263.0212	$263.02	$263.00	$263.00
Purchase #7	$189.63	5.208%	$199.5059	$199.51	$199.50	$199.50
7 purchase totals =	$1,080.72		$1,169.0043	$1,169.01	$1,168.95	$1,169.00