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	$181.61	5.267%	$191.1754	$191.18	$191.20	$191.20
Purchase #2	$72.63	12.289%	$81.5555	$81.56	$81.55	$81.60
Purchase #3	$172.55	8.704%	$187.5688	$187.57	$187.55	$187.60
Purchase #4	$105.42	8.609%	$114.4956	$114.50	$114.50	$114.50
Purchase #5	$153.83	8.857%	$167.4547	$167.45	$167.45	$167.50
Purchase #6	$35.77	7.160%	$38.3311	$38.33	$38.35	$38.30
Purchase #7	$141.91	12.499%	$159.6473	$159.65	$159.65	$159.60
7 purchase totals =	$863.72		$940.2284	$940.24	$940.25	$940.30