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	$99.60	10.354%	$109.9126	$109.91	$109.90	$109.90
Purchase #2	$199.53	9.632%	$218.7487	$218.75	$218.75	$218.70
Purchase #3	$155.58	5.424%	$164.0187	$164.02	$164.00	$164.00
Purchase #4	$107.79	3.375%	$111.4279	$111.43	$111.45	$111.40
Purchase #5	$158.61	5.858%	$167.9014	$167.90	$167.90	$167.90
Purchase #6	$205.36	3.138%	$211.8042	$211.80	$211.80	$211.80
Purchase #7	$230.94	6.107%	$245.0435	$245.04	$245.05	$245.00
7 purchase totals =	$1,157.41		$1,228.8570	$1,228.85	$1,228.85	$1,228.70