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	$153.55	13.656%	$174.5188	$174.52	$174.50	$174.50
Purchase #2	$62.66	7.611%	$67.4291	$67.43	$67.45	$67.40
Purchase #3	$249.56	12.302%	$280.2609	$280.26	$280.25	$280.30
Purchase #4	$132.49	12.831%	$149.4898	$149.49	$149.50	$149.50
Purchase #5	$119.46	4.250%	$124.5371	$124.54	$124.55	$124.50
Purchase #6	$153.68	4.604%	$160.7554	$160.76	$160.75	$160.80
Purchase #7	$100.44	4.413%	$104.8724	$104.87	$104.85	$104.90
7 purchase totals =	$971.84		$1,061.8635	$1,061.87	$1,061.85	$1,061.90