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	$124.34	5.429%	$131.0904	$131.09	$131.10	$131.10
Purchase #2	$82.86	7.546%	$89.1126	$89.11	$89.10	$89.10
Purchase #3	$61.59	11.134%	$68.4474	$68.45	$68.45	$68.40
Purchase #4	$57.40	11.291%	$63.881	$63.88	$63.90	$63.90
Purchase #5	$62.81	7.657%	$67.6194	$67.62	$67.60	$67.60
Purchase #6	$130.90	3.424%	$135.382	$135.38	$135.40	$135.40
Purchase #7	$187.32	3.785%	$194.4101	$194.41	$194.40	$194.40
7 purchase totals =	$707.22		$749.9429	$749.94	$749.95	$749.90