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	$171.69	11.278%	$191.0532	$191.05	$191.05	$191.10
Purchase #2	$85.95	12.539%	$96.7273	$96.73	$96.75	$96.70
Purchase #3	$98.43	11.563%	$109.8115	$109.81	$109.80	$109.80
Purchase #4	$214.62	5.206%	$225.7931	$225.79	$225.80	$225.80
Purchase #5	$99.78	11.861%	$111.6149	$111.61	$111.60	$111.60
Purchase #6	$249.64	11.580%	$278.5483	$278.55	$278.55	$278.50
Purchase #7	$97.66	8.361%	$105.8254	$105.83	$105.85	$105.80
7 purchase totals =	$1,017.77		$1,119.3737	$1,119.37	$1,119.40	$1,119.30