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	$77.99	5.595%	$82.3535	$82.35	$82.35	$82.40
Purchase #2	$211.55	8.649%	$229.847	$229.85	$229.85	$229.80
Purchase #3	$195.31	10.224%	$215.2785	$215.28	$215.30	$215.30
Purchase #4	$165.62	13.259%	$187.5796	$187.58	$187.60	$187.60
Purchase #5	$130.62	10.782%	$144.7034	$144.70	$144.70	$144.70
Purchase #6	$169.91	5.555%	$179.3485	$179.35	$179.35	$179.30
Purchase #7	$89.68	12.432%	$100.829	$100.83	$100.85	$100.80
7 purchase totals =	$1,040.68		$1,139.9395	$1,139.94	$1,140.00	$1,139.90