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	$145.49	3.812%	$151.0361	$151.04	$151.05	$151.00
Purchase #2	$210.39	7.113%	$225.355	$225.36	$225.35	$225.40
Purchase #3	$56.60	13.182%	$64.061	$64.06	$64.05	$64.10
Purchase #4	$132.70	13.604%	$150.7525	$150.75	$150.75	$150.80
Purchase #5	$110.75	3.783%	$114.9397	$114.94	$114.95	$114.90
Purchase #6	$54.48	3.482%	$56.377	$56.38	$56.40	$56.40
Purchase #7	$52.50	12.847%	$59.2447	$59.24	$59.25	$59.20
7 purchase totals =	$762.91		$821.7660	$821.77	$821.80	$821.80