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	$91.92	5.136%	$96.641	$96.64	$96.65	$96.60
Purchase #2	$75.89	8.812%	$82.5774	$82.58	$82.60	$82.60
Purchase #3	$116.60	10.412%	$128.7404	$128.74	$128.75	$128.70
Purchase #4	$33.32	6.535%	$35.4975	$35.50	$35.50	$35.50
Purchase #5	$55.78	10.162%	$61.4484	$61.45	$61.45	$61.40
Purchase #6	$168.52	10.872%	$186.8415	$186.84	$186.85	$186.80
Purchase #7	$213.95	10.206%	$235.7857	$235.79	$235.80	$235.80
7 purchase totals =	$755.98		$827.5319	$827.54	$827.60	$827.40