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	$72.29	13.770%	$82.2443	$82.24	$82.25	$82.20
Purchase #2	$170.57	10.732%	$188.8756	$188.88	$188.90	$188.90
Purchase #3	$133.45	8.853%	$145.2643	$145.26	$145.25	$145.30
Purchase #4	$150.98	10.850%	$167.3613	$167.36	$167.35	$167.40
Purchase #5	$17.54	5.539%	$18.5115	$18.51	$18.50	$18.50
Purchase #6	$242.62	7.551%	$260.9402	$260.94	$260.95	$260.90
Purchase #7	$236.33	8.141%	$255.5696	$255.57	$255.55	$255.60
7 purchase totals =	$1,023.78		$1,118.7668	$1,118.76	$1,118.75	$1,118.80