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	$82.55	10.395%	$91.1311	$91.13	$91.15	$91.10
Purchase #2	$76.50	3.345%	$79.0589	$79.06	$79.05	$79.10
Purchase #3	$107.35	4.634%	$112.3246	$112.32	$112.30	$112.30
Purchase #4	$48.75	10.521%	$53.879	$53.88	$53.90	$53.90
Purchase #5	$212.46	9.735%	$233.143	$233.14	$233.15	$233.10
Purchase #6	$209.75	5.299%	$220.8647	$220.86	$220.85	$220.90
Purchase #7	$109.78	9.768%	$120.5033	$120.50	$120.50	$120.50
7 purchase totals =	$847.14		$910.9046	$910.89	$910.90	$910.90