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	$198.78	3.559%	$205.8546	$205.85	$205.85	$205.90
Purchase #2	$102.74	8.532%	$111.5058	$111.51	$111.50	$111.50
Purchase #3	$21.40	3.551%	$22.1599	$22.16	$22.15	$22.20
Purchase #4	$180.53	4.603%	$188.8398	$188.84	$188.85	$188.80
Purchase #5	$86.57	11.759%	$96.7498	$96.75	$96.75	$96.70
Purchase #6	$37.73	3.525%	$39.06	$39.06	$39.05	$39.10
Purchase #7	$143.70	12.495%	$161.6553	$161.66	$161.65	$161.70
7 purchase totals =	$771.45		$825.8252	$825.83	$825.80	$825.90