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	$32.34	4.736%	$33.8716	$33.87	$33.85	$33.90
Purchase #2	$142.98	13.731%	$162.6126	$162.61	$162.60	$162.60
Purchase #3	$106.62	4.441%	$111.355	$111.36	$111.35	$111.40
Purchase #4	$104.71	9.710%	$114.8773	$114.88	$114.90	$114.90
Purchase #5	$171.50	4.423%	$179.0854	$179.09	$179.10	$179.10
Purchase #6	$89.55	7.519%	$96.2833	$96.28	$96.30	$96.30
Purchase #7	$146.91	10.664%	$162.5765	$162.58	$162.60	$162.60
7 purchase totals =	$794.61		$860.6617	$860.67	$860.70	$860.80