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	$192.97	7.332%	$207.1186	$207.12	$207.10	$207.10
Purchase #2	$167.41	8.471%	$181.5913	$181.59	$181.60	$181.60
Purchase #3	$132.86	10.310%	$146.5579	$146.56	$146.55	$146.60
Purchase #4	$36.77	4.700%	$38.4982	$38.50	$38.50	$38.50
Purchase #5	$77.27	6.826%	$82.5445	$82.54	$82.55	$82.50
Purchase #6	$67.59	3.108%	$69.6907	$69.69	$69.70	$69.70
Purchase #7	$176.71	8.243%	$191.2762	$191.28	$191.30	$191.30
7 purchase totals =	$851.58		$917.2774	$917.28	$917.30	$917.30