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	$104.65	4.379%	$109.2326	$109.23	$109.25	$109.20
Purchase #2	$224.46	3.207%	$231.6584	$231.66	$231.65	$231.70
Purchase #3	$135.96	6.462%	$144.7457	$144.75	$144.75	$144.70
Purchase #4	$69.28	4.361%	$72.3013	$72.30	$72.30	$72.30
Purchase #5	$211.77	11.689%	$236.5238	$236.52	$236.50	$236.50
Purchase #6	$215.48	11.535%	$240.3356	$240.34	$240.35	$240.30
Purchase #7	$69.84	9.334%	$76.3589	$76.36	$76.35	$76.40
7 purchase totals =	$1,031.44		$1,111.1563	$1,111.16	$1,111.15	$1,111.10