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	$175.66	3.302%	$181.4603	$181.46	$181.45	$181.50
Purchase #2	$52.89	11.807%	$59.1347	$59.13	$59.15	$59.10
Purchase #3	$59.36	8.207%	$64.2317	$64.23	$64.25	$64.20
Purchase #4	$49.46	9.737%	$54.2759	$54.28	$54.30	$54.30
Purchase #5	$203.35	7.723%	$219.0547	$219.05	$219.05	$219.10
Purchase #6	$215.27	10.512%	$237.8992	$237.90	$237.90	$237.90
Purchase #7	$90.51	5.434%	$95.4283	$95.43	$95.45	$95.40
7 purchase totals =	$846.50		$911.4848	$911.48	$911.55	$911.50