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	$33.60	10.311%	$37.0645	$37.06	$37.05	$37.10
Purchase #2	$115.46	8.728%	$125.5373	$125.54	$125.55	$125.50
Purchase #3	$9.73	7.157%	$10.4264	$10.43	$10.45	$10.40
Purchase #4	$235.73	13.626%	$267.8506	$267.85	$267.85	$267.90
Purchase #5	$99.91	5.841%	$105.7457	$105.75	$105.75	$105.70
Purchase #6	$42.30	3.770%	$43.8947	$43.89	$43.90	$43.90
Purchase #7	$34.30	4.697%	$35.9111	$35.91	$35.90	$35.90
7 purchase totals =	$571.03		$626.4303	$626.43	$626.45	$626.40