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	$119.72	7.682%	$128.9169	$128.92	$128.90	$128.90
Purchase #2	$153.69	11.698%	$171.6687	$171.67	$171.65	$171.70
Purchase #3	$81.90	9.511%	$89.6895	$89.69	$89.70	$89.70
Purchase #4	$50.38	13.196%	$57.0281	$57.03	$57.05	$57.00
Purchase #5	$189.34	6.381%	$201.4218	$201.42	$201.40	$201.40
Purchase #6	$5.81	11.620%	$6.4851	$6.49	$6.50	$6.50
Purchase #7	$54.88	13.654%	$62.3733	$62.37	$62.35	$62.40
7 purchase totals =	$655.72		$717.5834	$717.59	$717.55	$717.60