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	$207.72	12.186%	$233.0328	$233.03	$233.05	$233.00
Purchase #2	$82.25	3.523%	$85.1477	$85.15	$85.15	$85.10
Purchase #3	$108.28	6.512%	$115.3312	$115.33	$115.35	$115.30
Purchase #4	$143.86	5.734%	$152.1089	$152.11	$152.10	$152.10
Purchase #5	$221.89	7.225%	$237.9216	$237.92	$237.90	$237.90
Purchase #6	$130.26	11.208%	$144.8595	$144.86	$144.85	$144.90
Purchase #7	$87.83	13.365%	$99.5685	$99.57	$99.55	$99.60
7 purchase totals =	$982.09		$1,067.9702	$1,067.97	$1,067.95	$1,067.90