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	$130.59	12.265%	$146.6069	$146.61	$146.60	$146.60
Purchase #2	$231.25	3.630%	$239.6444	$239.64	$239.65	$239.60
Purchase #3	$132.98	11.585%	$148.3857	$148.39	$148.40	$148.40
Purchase #4	$153.65	7.563%	$165.2705	$165.27	$165.25	$165.30
Purchase #5	$76.66	12.286%	$86.0784	$86.08	$86.10	$86.10
Purchase #6	$234.34	4.665%	$245.272	$245.27	$245.25	$245.30
Purchase #7	$104.91	4.316%	$109.4379	$109.44	$109.45	$109.40
7 purchase totals =	$1,064.38		$1,140.6958	$1,140.70	$1,140.70	$1,140.70