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	$51.53	13.759%	$58.62	$58.62	$58.60	$58.60
Purchase #2	$171.31	12.618%	$192.9259	$192.93	$192.95	$192.90
Purchase #3	$67.52	6.275%	$71.7569	$71.76	$71.75	$71.80
Purchase #4	$239.79	11.244%	$266.752	$266.75	$266.75	$266.80
Purchase #5	$158.58	5.497%	$167.2971	$167.30	$167.30	$167.30
Purchase #6	$16.72	9.284%	$18.2723	$18.27	$18.25	$18.30
Purchase #7	$67.94	7.196%	$72.829	$72.83	$72.85	$72.80
7 purchase totals =	$773.39		$848.4532	$848.46	$848.45	$848.50