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	$111.76	13.358%	$126.6889	$126.69	$126.70	$126.70
Purchase #2	$181.48	3.837%	$188.4434	$188.44	$188.45	$188.40
Purchase #3	$156.61	10.324%	$172.7784	$172.78	$172.80	$172.80
Purchase #4	$204.27	4.124%	$212.6941	$212.69	$212.70	$212.70
Purchase #5	$177.96	4.659%	$186.2512	$186.25	$186.25	$186.30
Purchase #6	$175.48	4.598%	$183.5486	$183.55	$183.55	$183.50
Purchase #7	$141.87	7.367%	$152.3216	$152.32	$152.30	$152.30
7 purchase totals =	$1,149.43		$1,222.7262	$1,222.72	$1,222.75	$1,222.70