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	$192.94	11.700%	$215.514	$215.51	$215.50	$215.50
Purchase #2	$223.57	11.847%	$250.0563	$250.06	$250.05	$250.10
Purchase #3	$81.36	12.481%	$91.5145	$91.51	$91.50	$91.50
Purchase #4	$38.54	7.559%	$41.4532	$41.45	$41.45	$41.50
Purchase #5	$119.97	3.211%	$123.8222	$123.82	$123.80	$123.80
Purchase #6	$199.25	9.415%	$218.0094	$218.01	$218.00	$218.00
Purchase #7	$28.32	12.641%	$31.8999	$31.90	$31.90	$31.90
7 purchase totals =	$883.95		$972.2695	$972.26	$972.20	$972.30