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	$138.69	10.111%	$152.7129	$152.71	$152.70	$152.70
Purchase #2	$219.37	3.434%	$226.9032	$226.90	$226.90	$226.90
Purchase #3	$62.97	5.541%	$66.4592	$66.46	$66.45	$66.50
Purchase #4	$115.72	6.424%	$123.1539	$123.15	$123.15	$123.20
Purchase #5	$167.75	6.782%	$179.1268	$179.13	$179.15	$179.10
Purchase #6	$50.49	13.148%	$57.1284	$57.13	$57.15	$57.10
Purchase #7	$229.35	11.322%	$255.317	$255.32	$255.30	$255.30
7 purchase totals =	$984.34		$1,060.8014	$1,060.80	$1,060.80	$1,060.80