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	$89.41	12.668%	$100.7365	$100.74	$100.75	$100.70
Purchase #2	$213.98	12.737%	$241.2346	$241.23	$241.25	$241.20
Purchase #3	$39.48	4.544%	$41.274	$41.27	$41.25	$41.30
Purchase #4	$139.68	4.229%	$145.5871	$145.59	$145.60	$145.60
Purchase #5	$201.33	12.676%	$226.8506	$226.85	$226.85	$226.90
Purchase #6	$231.71	10.347%	$255.685	$255.69	$255.70	$255.70
Purchase #7	$161.38	5.248%	$169.8492	$169.85	$169.85	$169.80
7 purchase totals =	$1,076.97		$1,181.2170	$1,181.22	$1,181.25	$1,181.20