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	$218.56	8.658%	$237.4829	$237.48	$237.50	$237.50
Purchase #2	$138.66	10.589%	$153.3427	$153.34	$153.35	$153.30
Purchase #3	$189.29	5.213%	$199.1577	$199.16	$199.15	$199.20
Purchase #4	$80.64	12.488%	$90.7103	$90.71	$90.70	$90.70
Purchase #5	$51.31	5.207%	$53.9817	$53.98	$54.00	$54.00
Purchase #6	$173.83	6.579%	$185.2663	$185.27	$185.25	$185.30
Purchase #7	$204.63	9.477%	$224.0228	$224.02	$224.00	$224.00
7 purchase totals =	$1,056.92		$1,143.9644	$1,143.96	$1,143.95	$1,144.00