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	$39.51	13.209%	$44.7289	$44.73	$44.75	$44.70
Purchase #2	$59.28	13.576%	$67.3279	$67.33	$67.35	$67.30
Purchase #3	$144.55	9.542%	$158.343	$158.34	$158.35	$158.30
Purchase #4	$31.25	12.183%	$35.0572	$35.06	$35.05	$35.10
Purchase #5	$155.56	3.426%	$160.8895	$160.89	$160.90	$160.90
Purchase #6	$56.61	4.866%	$59.3646	$59.36	$59.35	$59.40
Purchase #7	$124.71	12.407%	$140.1828	$140.18	$140.20	$140.20
7 purchase totals =	$611.47		$665.8939	$665.89	$665.95	$665.90