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	$154.68	9.152%	$168.8363	$168.84	$168.85	$168.80
Purchase #2	$250.91	4.357%	$261.8421	$261.84	$261.85	$261.80
Purchase #3	$174.94	9.334%	$191.2689	$191.27	$191.25	$191.30
Purchase #4	$157.72	6.421%	$167.8472	$167.85	$167.85	$167.80
Purchase #5	$244.40	7.393%	$262.4685	$262.47	$262.45	$262.50
Purchase #6	$89.85	3.272%	$92.7899	$92.79	$92.80	$92.80
Purchase #7	$19.83	6.376%	$21.0944	$21.09	$21.10	$21.10
7 purchase totals =	$1,092.33		$1,166.1473	$1,166.15	$1,166.15	$1,166.10