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	$137.80	11.309%	$153.3838	$153.38	$153.40	$153.40
Purchase #2	$188.29	8.272%	$203.8653	$203.87	$203.85	$203.90
Purchase #3	$96.96	3.369%	$100.2266	$100.23	$100.25	$100.20
Purchase #4	$96.41	9.340%	$105.4147	$105.41	$105.40	$105.40
Purchase #5	$219.36	5.460%	$231.3371	$231.34	$231.35	$231.30
Purchase #6	$222.43	3.393%	$229.977	$229.98	$230.00	$230.00
Purchase #7	$179.50	9.450%	$196.4628	$196.46	$196.45	$196.50
7 purchase totals =	$1,140.75		$1,220.6673	$1,220.67	$1,220.70	$1,220.70