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	$112.28	5.355%	$118.2926	$118.29	$118.30	$118.30
Purchase #2	$112.78	12.217%	$126.5583	$126.56	$126.55	$126.60
Purchase #3	$156.73	7.467%	$168.433	$168.43	$168.45	$168.40
Purchase #4	$204.32	3.293%	$211.0483	$211.05	$211.05	$211.00
Purchase #5	$148.40	3.533%	$153.643	$153.64	$153.65	$153.60
Purchase #6	$243.89	10.604%	$269.7521	$269.75	$269.75	$269.80
Purchase #7	$118.48	11.669%	$132.3054	$132.31	$132.30	$132.30
7 purchase totals =	$1,096.88		$1,180.0327	$1,180.03	$1,180.05	$1,180.00