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	$56.69	5.290%	$59.6889	$59.69	$59.70	$59.70
Purchase #2	$110.33	3.855%	$114.5832	$114.58	$114.60	$114.60
Purchase #3	$122.84	11.617%	$137.1103	$137.11	$137.10	$137.10
Purchase #4	$77.28	3.648%	$80.0992	$80.10	$80.10	$80.10
Purchase #5	$75.50	13.536%	$85.7197	$85.72	$85.70	$85.70
Purchase #6	$22.83	3.208%	$23.5624	$23.56	$23.55	$23.60
Purchase #7	$59.72	7.636%	$64.2802	$64.28	$64.30	$64.30
7 purchase totals =	$525.19		$565.0439	$565.04	$565.05	$565.10