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	$220.56	3.683%	$228.6832	$228.68	$228.70	$228.70
Purchase #2	$187.39	4.731%	$196.2554	$196.26	$196.25	$196.30
Purchase #3	$27.50	4.784%	$28.8156	$28.82	$28.80	$28.80
Purchase #4	$203.68	10.131%	$224.3148	$224.31	$224.30	$224.30
Purchase #5	$39.72	4.773%	$41.6158	$41.62	$41.60	$41.60
Purchase #6	$53.63	7.333%	$57.5627	$57.56	$57.55	$57.60
Purchase #7	$189.40	5.588%	$199.9837	$199.98	$200.00	$200.00
7 purchase totals =	$921.88		$977.2312	$977.23	$977.20	$977.30