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	$89.46	7.872%	$96.5023	$96.50	$96.50	$96.50
Purchase #2	$81.67	4.637%	$85.457	$85.46	$85.45	$85.50
Purchase #3	$218.31	10.832%	$241.9573	$241.96	$241.95	$242.00
Purchase #4	$185.41	10.710%	$205.2674	$205.27	$205.25	$205.30
Purchase #5	$15.77	5.109%	$16.5757	$16.58	$16.60	$16.60
Purchase #6	$99.38	11.473%	$110.7819	$110.78	$110.80	$110.80
Purchase #7	$78.65	13.425%	$89.2088	$89.21	$89.20	$89.20
7 purchase totals =	$768.65		$845.7504	$845.76	$845.75	$845.90