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	$159.72	10.382%	$176.3021	$176.30	$176.30	$176.30
Purchase #2	$169.55	5.728%	$179.2618	$179.26	$179.25	$179.30
Purchase #3	$115.83	4.859%	$121.4582	$121.46	$121.45	$121.50
Purchase #4	$166.49	5.397%	$175.4755	$175.48	$175.50	$175.50
Purchase #5	$102.91	8.274%	$111.4248	$111.42	$111.40	$111.40
Purchase #6	$54.77	5.616%	$57.8459	$57.85	$57.85	$57.80
Purchase #7	$242.31	8.404%	$262.6737	$262.67	$262.65	$262.70
7 purchase totals =	$1,011.58		$1,084.4420	$1,084.44	$1,084.40	$1,084.50