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	$79.72	8.333%	$86.3631	$86.36	$86.35	$86.40
Purchase #2	$242.36	8.555%	$263.0939	$263.09	$263.10	$263.10
Purchase #3	$203.96	6.512%	$217.2419	$217.24	$217.25	$217.20
Purchase #4	$209.99	11.173%	$233.4522	$233.45	$233.45	$233.50
Purchase #5	$48.47	12.634%	$54.5937	$54.59	$54.60	$54.60
Purchase #6	$71.36	9.360%	$78.0393	$78.04	$78.05	$78.00
Purchase #7	$158.83	6.263%	$168.7775	$168.78	$168.80	$168.80
7 purchase totals =	$1,014.69		$1,101.5616	$1,101.55	$1,101.60	$1,101.60