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	$174.56	12.620%	$196.5895	$196.59	$196.60	$196.60
Purchase #2	$111.76	4.192%	$116.445	$116.45	$116.45	$116.40
Purchase #3	$144.41	4.205%	$150.4824	$150.48	$150.50	$150.50
Purchase #4	$61.76	4.582%	$64.5898	$64.59	$64.60	$64.60
Purchase #5	$117.67	4.305%	$122.7357	$122.74	$122.75	$122.70
Purchase #6	$112.83	12.492%	$126.9247	$126.92	$126.90	$126.90
Purchase #7	$107.42	6.806%	$114.731	$114.73	$114.75	$114.70
7 purchase totals =	$830.41		$892.4981	$892.50	$892.55	$892.40