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	$127.45	11.680%	$142.3362	$142.34	$142.35	$142.30
Purchase #2	$57.34	10.540%	$63.3836	$63.38	$63.40	$63.40
Purchase #3	$175.67	11.774%	$196.3534	$196.35	$196.35	$196.40
Purchase #4	$91.81	8.138%	$99.2815	$99.28	$99.30	$99.30
Purchase #5	$77.37	9.641%	$84.8292	$84.83	$84.85	$84.80
Purchase #6	$116.73	12.459%	$131.2734	$131.27	$131.25	$131.30
Purchase #7	$54.34	5.157%	$57.1423	$57.14	$57.15	$57.10
7 purchase totals =	$700.71		$774.5996	$774.59	$774.65	$774.60