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	$96.73	7.291%	$103.7826	$103.78	$103.80	$103.80
Purchase #2	$158.73	3.791%	$164.7475	$164.75	$164.75	$164.70
Purchase #3	$185.40	6.236%	$196.9615	$196.96	$196.95	$197.00
Purchase #4	$207.46	7.560%	$223.144	$223.14	$223.15	$223.10
Purchase #5	$145.82	6.871%	$155.8393	$155.84	$155.85	$155.80
Purchase #6	$104.38	5.417%	$110.0343	$110.03	$110.05	$110.00
Purchase #7	$158.25	6.757%	$168.943	$168.94	$168.95	$168.90
7 purchase totals =	$1,056.77		$1,123.4522	$1,123.44	$1,123.50	$1,123.30