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	$58.27	5.417%	$61.4265	$61.43	$61.45	$61.40
Purchase #2	$146.80	10.820%	$162.6838	$162.68	$162.70	$162.70
Purchase #3	$222.54	12.425%	$250.1906	$250.19	$250.20	$250.20
Purchase #4	$172.91	13.653%	$196.5174	$196.52	$196.50	$196.50
Purchase #5	$41.47	11.449%	$46.2179	$46.22	$46.20	$46.20
Purchase #6	$121.90	8.396%	$132.1347	$132.13	$132.15	$132.10
Purchase #7	$163.70	11.418%	$182.3913	$182.39	$182.40	$182.40
7 purchase totals =	$927.59		$1,031.5622	$1,031.56	$1,031.60	$1,031.50