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	$217.85	10.581%	$240.9007	$240.90	$240.90	$240.90
Purchase #2	$211.94	6.783%	$226.3159	$226.32	$226.30	$226.30
Purchase #3	$176.50	8.556%	$191.6013	$191.60	$191.60	$191.60
Purchase #4	$20.45	3.238%	$21.1122	$21.11	$21.10	$21.10
Purchase #5	$105.54	11.678%	$117.865	$117.87	$117.85	$117.90
Purchase #6	$145.71	3.512%	$150.8273	$150.83	$150.85	$150.80
Purchase #7	$231.50	5.179%	$243.4894	$243.49	$243.50	$243.50
7 purchase totals =	$1,109.49		$1,192.1118	$1,192.12	$1,192.10	$1,192.10