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	$90.67	8.179%	$98.0859	$98.09	$98.10	$98.10
Purchase #2	$43.83	3.558%	$45.3895	$45.39	$45.40	$45.40
Purchase #3	$226.60	6.126%	$240.4815	$240.48	$240.50	$240.50
Purchase #4	$219.26	4.303%	$228.6948	$228.69	$228.70	$228.70
Purchase #5	$185.68	5.826%	$196.4977	$196.50	$196.50	$196.50
Purchase #6	$114.96	11.435%	$128.1057	$128.11	$128.10	$128.10
Purchase #7	$237.48	13.611%	$269.8034	$269.80	$269.80	$269.80
7 purchase totals =	$1,118.48		$1,207.0585	$1,207.06	$1,207.10	$1,207.10