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	$99.68	9.333%	$108.9831	$108.98	$109.00	$109.00
Purchase #2	$91.50	11.397%	$101.9283	$101.93	$101.95	$101.90
Purchase #3	$79.96	7.306%	$85.8019	$85.80	$85.80	$85.80
Purchase #4	$79.89	13.684%	$90.8221	$90.82	$90.80	$90.80
Purchase #5	$102.40	9.274%	$111.8966	$111.90	$111.90	$111.90
Purchase #6	$96.61	8.615%	$104.933	$104.93	$104.95	$104.90
Purchase #7	$181.48	13.339%	$205.6876	$205.69	$205.70	$205.70
7 purchase totals =	$731.52		$810.0526	$810.05	$810.10	$810.00