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	$119.60	6.791%	$127.722	$127.72	$127.70	$127.70
Purchase #2	$110.62	8.831%	$120.3889	$120.39	$120.40	$120.40
Purchase #3	$100.81	8.427%	$109.3053	$109.31	$109.30	$109.30
Purchase #4	$196.37	9.558%	$215.139	$215.14	$215.15	$215.10
Purchase #5	$136.67	5.716%	$144.4821	$144.48	$144.50	$144.50
Purchase #6	$233.28	10.121%	$256.8903	$256.89	$256.90	$256.90
Purchase #7	$166.43	7.282%	$178.5494	$178.55	$178.55	$178.50
7 purchase totals =	$1,063.78		$1,152.4770	$1,152.48	$1,152.50	$1,152.40