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	$129.69	4.215%	$135.1564	$135.16	$135.15	$135.20
Purchase #2	$156.48	12.357%	$175.8162	$175.82	$175.80	$175.80
Purchase #3	$143.86	10.140%	$158.4474	$158.45	$158.45	$158.40
Purchase #4	$102.66	8.849%	$111.7444	$111.74	$111.75	$111.70
Purchase #5	$95.72	3.253%	$98.8338	$98.83	$98.85	$98.80
Purchase #6	$113.44	8.689%	$123.2968	$123.30	$123.30	$123.30
Purchase #7	$235.88	5.296%	$248.3722	$248.37	$248.35	$248.40
7 purchase totals =	$977.73		$1,051.6672	$1,051.67	$1,051.65	$1,051.60