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	$78.57	4.697%	$82.2604	$82.26	$82.25	$82.30
Purchase #2	$27.67	6.768%	$29.5427	$29.54	$29.55	$29.50
Purchase #3	$129.57	12.498%	$145.7637	$145.76	$145.75	$145.80
Purchase #4	$211.88	9.415%	$231.8285	$231.83	$231.85	$231.80
Purchase #5	$166.96	11.779%	$186.6262	$186.63	$186.65	$186.60
Purchase #6	$78.98	3.310%	$81.5942	$81.59	$81.60	$81.60
Purchase #7	$247.74	10.260%	$273.1581	$273.16	$273.15	$273.20
7 purchase totals =	$941.37		$1,030.7738	$1,030.77	$1,030.80	$1,030.80